01 Ponder : Weekly Reflection

edited Aug 10 '13 at 15:15

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Benjamin

11.8k1696179

asked Mar 11 '09 at 0:03

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Marius

36.9k18102128

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4 Answers

(from http://www.w3schools.com/ajax/ajax_xmlhttprequest_onreadystatechange.asp)

[up vote]( "This answer is useful")144[down vote]( "This answer is not useful")accepted

The full list of readyState values is:

State Description 0 The request is not initialized 1 The request has been set up 2 The request has been sent 3 The request is in process 4 The request is complete

In practice you almost never use any of them except for 4.

Some XMLHttpRequest implementations may let you see partially received responses in responseText when readyState==3, but this isn't universally supported and shouldn't be relied upon.

What is an endpoint?

http://stackoverflow.com/questions/2122604/what-is-an-endpoint

"n endpoint is a URL pattern used to communicate with an API."

To support server-to-server interactions, first create a service account for your project in the API Console. If you want to access user data for users in your G Suite domain, then delegate domain-wide access to the service account.

Then, your application prepares to make authorized API calls by using the service account's credentials to request an access token from the OAuth 2.0 auth server.

Finally, your application can use the access token to call Google APIs.

What does this mean?

“...using the service account's credentials to request an access token from the OAuth 2.0 auth server."

And this?

After you obtain the client ID and private key from the API Console, your application needs to complete the following steps:

Create a JSON Web Token (JWT, pronounced "jot"), which includes a header, a claim set, and a signature.

Request an access token from the Google OAuth 2.0 Authorization Server.
Handle the JSON response that the Authorization Server returns.

myBack needs to wrap to 3 when it is 0….

CORRECTION: Actually no. 0 is correct. BUT when it is returning data from the index, it is returning delta instead of alfa. Not sure why. Is it stored wrong? Is that why the copy constructor is important?

WAIT! Screenshots show that myFront needs to be 1, according to Willis’s code….

So I'm working on the win condition for BugTag. Requirements:

If bugs touch, the chaser wins.
If time runs out, the chaser wins? Maybe? Or is it a tie?

Here's some things I'm gonna need to pull it off:

Win.java.class
boolean isChaser = rand.nextBoolean(); line 36, GridObjectHandler.java
the position of the bugs at the present time
needs to check to see if they're touching all the time, like maybe part of a callback? function

This looks important...

else if (gameState == GAME_OVER)
        {
            batch.begin();

            bugGame.draw(batch);

            displayTime();

            displayMessage();

            //Set winner variable too. The first frame
            // won't have the result but that should be fine

            //Do something with SharedPrefs,
            //like setting the high score, etc.

            batch.end();
        }

Bug #1 (or BugOne) is the chaser. At least at first.

maybe add a getPosition() method to the Bug.java class.... CORRECTION: already there, extended from GridObject. Just reference it from a Bug object. ###Question But where are the Bug objects initialized? ###Answer They're initialized in GridObjectHandler(). But in order to use Win.checkWin(), we need to instantiate a new Bug in MainGame, and then pass it to GridObjectHandler in a constructor so it can be added to the gridObjects via gridObjects.add.

###TODO: we should specify at the beginning of the game who is the chaser ###(19, 54) GridPoint2 currentPosition = new GridPoint2(); //todo: this should seriously be private. But a lot of methods depend on this so it might take some work. -Cameron ###Todo: why do we get and set the gameState from ButtonProcessor? Doesn't make a whole lot of sense. Maybe gameState should be in it's own class?

###todo: make trello team and add it to slack to track stuff.

###TODO: when timer runs out, text should include which color bug won. "Yellow Bug won!"

Before we start In this tutorial we will cover how to create basic templates and what is so great about using templates, as well as how to add operator overloads to classes you create.

To do this we will be creating a simple Account class that will allow for different types of data to be inputted.

Starting out To start off lets learn how to create templates.

Create a new C++ file and type in the standard headers:

1``#include <iostream>

2``using namespace std;

To specify something is a template you need to create a class like so:

1``template <``class T>

2``class Account{

3`` ``//stuff here

4``};

This creates the class called Account and tell it that it works as a template with the type called T.

Now that we have the simple class complete lets start filling things out. First off we will need a variable to use for the amount of money (or whatever) that is in the account. This is done like so:

1``template <``class T>

2``class Account{

3``private``:

4`` ``T amount;

5``};

This creates the variable amount of type T, simple enough. At this point in time you are probably starting to see how to specify data types through templates, so lets finish off the class (It needs to have a constructor, and a function that returns the amount):

01``template <``class T>

02``class Account{

03``private``:

04`` ``T amount;

05``public``:

06`` ``Account(``void``){

07`` ``amount = 0;

08`` ``}

09`` ``Account(T initialValue){

10`` ``amount = initialValue;

11`` ``}

12`` ``T getAmount(``void``){

13`` ``return amount;

14`` ``}

15``};

You will notice the 2 contructors. This is known as constructor overloading, and basically acts like a check for different information being sent into the class constructor. Basically, if you call the constructor with no arguments it will set the amount to 0, otherwise, if a value with the datatype T is sent into the constructor it sets amount to the value sent in.

The main function Now that we have the class basics in place we will create the main function to allow us to create multiple calls to our Account class with different datatypes.

Here is the main in full:

1``int main(``void``){

2`` ``typedef Account<``int``> intAccount;

3`` ``intAccount test(1000);

4`` ``cout << ``"Current balance: " << test.getAmount() << ``endl``;

5`` ``return 0;

6``}

NOTICE - We are using typedef to say every Account of type int can be known as the datatype of intAccount. This makes things very easy because you could create multiple types of Account quickly.

If we wanted to also have an Account with the amount datatype of float we would do something like so:

1``int main(``void``){

2`` ``typedef Account<``int``> intAccount;

3`` ``typedef Account<``float``> floatAccount;

4`` ``intAccount test(1000);

5`` ``floatAccount test2(3.1415);

6`` ``cout << ``"Current int balance: " << test.getAmount() << ``endl``; ``// outputs 1000

7`` ``cout << ``"Current float balance: " << test2.getAmount() << ``endl``; ``// outputs 3.1415

8`` ``return 0;

9``}

You can also create multiple instances of the class with a single typedef like so:

1``int main(``void``){

2`` ``typedef Account<``int``> intAccount;

3`` ``intAccount test(1000);

4`` ``intAccount test2(314);

5`` ``cout << ``"Current int balance: " << test.getAmount() << ``endl``; ``// outputs 1000

6`` ``cout << ``"Current int balance2: " << test2.getAmount() << ``endl``; ``// outputs 314

7`` ``return 0;

8``}

NOTICE - We have test2 as an integer now, instead of a float.

Operator Overloading Operator overloading allows us to overload operators (as the name would suggest) for classes etc. Here we will take a look at how to set the amount held in our Account class by overloading the = operator for our class.

01``template <``class T>

02``class Account{

03``private``:

04`` ``T amount;

05``public``:

06`` ``Account(``void``){

07`` ``amount = 0;

08`` ``}

09`` ``Account(T initialValue){

10`` ``amount = initialValue;

11`` ``}

12`` ``T getAmount(``void``){

13`` ``return amount;

14`` ``}

15`` ``void operator=(T newVal){

16`` ``amount = newVal;

17`` ``}

18``};

Yes, those three lines of code overloaded the = operator for Account so, now we can make quick updates to the amount help in our instance of the class like so:

1``int main(``void``){

2`` ``typedef Account<``int``> intAccount;

3`` ``intAccount test(1000);

4`` ``intAccount test2(314);

5`` ``test2 = 900;

6`` ``cout << ``"Current int balance: " << test.getAmount() << ``endl``; ``// outputs 1000

7`` ``cout << ``"Current int balance2: " << test2.getAmount() << ``endl``; ``// outputs 900

8`` ``return 0;

9``}

Wrapping up Here is a full code I have created that allows for more operator overloads, and an example of it working:

01``#include <iostream>

02``using namespace std;

03

04``template <``class T>

05``class Account{

06``private``:

07`` ``T amount;

08``public``:

09`` ``Account(T initAmt){

10`` ``amount = initAmt;

11`` ``}

12`` ``Account(``void``){

13`` ``amount = 0;

14`` ``}

15`` ``~Account(``void``){

16`` ``}

17`` ``T getAmt(``void``){

18`` ``return amount;

19`` ``}

20`` ``void operator=(T newVal){

21`` ``amount = newVal;

22`` ``}

23`` ``void operator+=(T addVal){

24`` ``amount += addVal;

25`` ``}

26`` ``void operator-=(T subVal){

27`` ``amount -= subVal;

28`` ``}

29`` ``void operator*=(T multVal){

30`` ``amount *= multVal;

31`` ``}

32`` ``void operator/=(T divVal){

33`` ``amount /= divVal;

34`` ``}

35

36``};

37

38``int main(``void``){

39`` ``typedef Account<``int``> intAccount;

40`` ``intAccount test(1000);

41`` ``test = 12354;

42`` ``test += 10;

43`` ``cout << ``"Current balance: " << test.getAmt() << ``endl``;

44`` ``return 0;

45``}

The end Hope you all got something out of this.

Title: Error in IntelliJ.

Solution:

import android.view.View.OnClickListener;

OR use View.OnClickListener.

“cannot resolve symbol R” in Android Studio

Ask Question

[up vote]( "This question shows research effort; it is useful and clear")392[down vote]( "This question does not show any research effort; it is unclear or not useful")favorite

98

In every instance in all of my classes where I reference R.id.something, the R is in red and it says "cannot resolve symbol R". Also every time there is R.layout.something it is underlined in red and says "cannot resolve method setContentView(?)". The project always builds fine. It is annoying to see this all the time. I have read many other questions on here about something similar but most involved importing projects from eclipse. I am using what I believe to be the most recent version of android studio and the project was created with android studio and worked without any cannot resolve R problems. I would like to know what causes this if anyone knows.

UPDATE: Solution: At the time android studio was brand new and I was also a brand new developer. I should never had been using android studio, I never realized how unfinished it was. Thanks everyone for the support in trying to help since this has been posted. Ironically the actual answer to this question has been deleted and cannot be undeleted. I feel that my original answer is the solution to this problem.

My original answer that was deleted:

I think I have figured out the issue. The issue is with Android Studio, every time I added the admob library all these errors started. All my other projects without ads don't have similar issues. I'm now using Intelij and staying away from Android Studio

android android-studio r.java-file

edited Dec 8 '16 at 14:34

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Suragch

80.9k43322388

asked Jun 11 '13 at 21:18

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ez4nick

2,04482340

We're looking for long answers that provide some explanation and context. Don't just give a one-line answer; explain why your answer is right, ideally with citations. Answers that don't include explanations may be removed.

2

i searched many times before asking this question and found many similar questions including the one you mentioned. i did read the suggestion in that question and there is no import Android.R in any of my java files. – ez4nick Jun 11 '13 at 21:50

2

Hey everyone I forgot about asking this question since it was asked so long ago. I should have accepted my own answer a year ago that is now the comment above this. The issue was with simply that android studio was in such an early stage at the time and as a new developer I never should have never been using it. Rest assured everything is working fine now and has been. If it is possible please undelete my original answer so I can accept it. – ez4nick Nov 21 '14 at 3:26

1

Not finding R isnt your error its an error caused by a Build fault Fix your other errors and you should be fine. – Just_someone Sep 26 '16 at 11:26

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51 Answers

1 2 next

[up vote]( "This answer is useful")489[down vote]( "This answer is not useful")

I had this this issue too. A simple 'gradlew clean' and 'gradlew build' did the trick.

Click on Build->Clean Project and that will perform a gradle clean

edited Feb 23 '15 at 14:29

[

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tokhi

7,772116181

answered Aug 12 '13 at 9:30

[

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Vipassana Vijayarangan

5,3892818

23

some times you also need to restart android studio. or at least for me. – Foo Bar User Feb 12 '14 at 0:47

3

You execute it from the command line – Jay Sidri Mar 12 '14 at 4:25

15

For those who convulse over using the command line, click on Build->Clean Project and that will perform a 'gradlew clean'. ;) – Mr. Concolato Mar 31 '14 at 19:44

10

No luck...The cleaning rebuilding doesn't working fr me – CandleCoder Jan 7 '16 at 1:37

show 5 more comments

[up vote]( "This answer is useful")153[down vote]( "This answer is not useful")

In the latest versions of Android Studio, at least for me, the following works:

"Tools" -> "Android" -> "Sync Project with Gradle Files"

http://jordan.byui.edu/~ercanbracks/nowServing/queue/index.php

For your review and consideration.

You do NOT have to use this code.

/***************************************************
* QUEUE :: PUSH
* Add item on the end of the vector. If full, double
* capacity.
**************************************************/
template <class T>
void Queue <T> :: push(const T & t) throw (const char *)
{
   int newCap = 0;
   int oldCap = maxSize;
   int newBack = myBack + 1;
   if (maxSize > 0)
   newBack =  (myBack + 1) % maxSize;
   
   // check if empty or full (still maintaining a blank space)
   // then update capacity
   if (maxSize == 0 || abs(size() - maxSize) == 0)
   {
    if (maxSize == 0)
     newCap = 4; // default to 4
      else
       newCap = (maxSize * 2);
   
      //copy data into temp
    T *tempData = new T[maxSize];
    int j = 0;
    for (int i = 0; i < size(); i++) 
    {
       int index = (i + myFront) % size();
       tempData[i] = data[index];
    }
      
      // attempt to allocate
      try
      {
         data = NULL;
         delete[] data;
         data = new T[newCap + 1];
         maxSize = newCap;

         //after reallocating space, correct myBack and myFront
         myBack = numItems;
         newBack = (myBack + 1) % maxSize;
         myFront = 0;

         //copy tempData into newly allocated data
         int i;
         for (i = 0; i < numItems; i++)
         {
            data[i] = tempData[i];
         }
         
         delete[] tempData; // free memory allocated for temp data
         tempData - NULL;  //prevent deallocated memory from being used.
      }
      catch (std::bad_alloc)
      {
         throw "ERROR: Unable to allocate a new buffer for queue";
      }
   }

   //add new value at end
   data[myBack] = t;
   myBack = newBack;
   numItems++;
   
   return;
}

/***************************************************
* QUEUE :: POP
* Removes an item from the head of the queue, serving 
* to reduce the size by one. Note that if the queue is 
* already empty, the following c-string exception will 
* be thrown: ERROR: attempting to pop from an empty queue
****************************************************/
template <class T>
void Queue<T> ::  pop() throw (const char *)
{
   if (empty())
   {
      throw "ERROR: attempting to pop from an empty queue";
   }
   else
   {
      myFront = (myFront + 1) % maxSize;
      numItems--;
   }
}

a good question from StackOverflow. One that I also have had.

If I override operator= will the copy constructor automatically use the new operator? Similarly, if I define a copy constructor, will operator= automatically 'inherit' the behavior from the copy constructor?

Answer:

No, they are different operators.

The copy constructor is for creating a new object. It copies a existing object to a newly constructed object.The copy constructor is used to initialize a new instance from an old instance. It is not necessarily called when passing variables by value into functions or as return values out of functions.

The assignment operator is to deal with an already existing object. The assignment operator is used to change an existing instance to have the same values as the rvalue, which means that the instance has to be destroyed and re-initialized if it has internal dynamic memory.

Useful link :

Copy Constructors, Assignment Operators, and More

Copy constructor and = operator overload in C++: is a common function possible?

ul>li selects all li that are a direct child of ul whereas ul li selects all li that are anywhere within (descending as deep as you like) a ul

For HTML:

\<ul\> \<li\>\<span\>\<a href='\#'\>Something\</a\>\</span\>\</li\> \<li\>\<a href='\#'\>or Other\</a\>\</li\> \</ul\>

And CSS:

li a{ color: green; } li\>a{ color: red; }

The colour of Something will remain green but or Other will be red

Git is a powerful decentralized revision control system, and is the means for deploying apps to Heroku. You don’t need to be proficient with Git to use it for deploying code to Heroku, but you may find it valuable to learn the basics.

Tracking your app in git

Heroku apps expect the app directory structure at the root of the repository. If your app is inside a subdirectory in your repository, it won’t run when pushed to Heroku.

Before you can push an app to Heroku, you’ll need to initialize a local Git repository and commit your files to it. For example, if you have an app in a directory, myapp, then create a new repository for it:

$ cd myapp $ git init Initialized empty Git repository in .git/ $ git add . $ git commit -m "my first commit" Created initial commit 5df2d09: my first commit  44 files changed, 8393 insertions(+), 0 deletions(-)  create mode 100644 README  create mode 100644 Procfile  create mode 100644 app/controllers/source\_file ...

This is a local repository, now residing inside the .git directory. Nothing has been sent anywhere yet; you’ll need to create a remote and do a push to deploy your code to Heroku.

Creating a Heroku remote

Git remotes are references to remote repositories. You can have any number of these, but for now we’ll focus on just the remote to Heroku. The heroku create command creates a new application on Heroku – along with a git remote that must be used to receive your application source.

$ heroku create Creating falling-wind-1624... done, stack is cedar-14 http://falling-wind-1624.herokuapp.com/ | https://git.heroku.com/falling-wind-1624.git Git remote heroku added

By default, Heroku configures HTTP as the Git transport. The Heroku CLI will automatically place credentials in the .netrc file on heroku login. The Git client uses cURL when interacting with HTTP remotes, and cURL will use the credentials from the .netrc file. See the Authentication section and the CLI authentication article for details.

You can verify the remote in your git configuration as well:

$ git remote -v heroku https://git.heroku.com/falling-wind-1624.git (fetch) heroku https://git.heroku.com/falling-wind-1624.git (push)

You can also take an existing Git repository and add a remote using the git URL provided when you created your app. You may need to do this to associate a Git repository with an existing application. The heroku git:remote command will add this remote for you based on your applications git url.

$ heroku git:remote -a falling-wind-1624 Git remote heroku added.

The remote is named heroku in this example, but you can name the remote anything you want by passing -r other_remote_name. You may find it easier to follow the examples if you stick to using the heroku remote rather than using one with a different name.

There is one special remote name: origin, which is the default for pushes. Using origin as the remote name will allow you to type just git push instead of git push heroku, but we recommend using an explicitly named remote.

To switch from SSH Git to HTTP Git, run heroku git:remote in the directory holding your local Git repository. The CLI will override the heroku Git remote to use the HTTP protocol.

Deploying code

Your Heroku app starts with a blank repository – it has no branches and no code. So the first time you deploy, you’ll need to specify a remote branch to push to. You can do your first push:

$ git push heroku master Initializing repository, done. updating 'refs/heads/master' ...

This will push your code to the heroku remote, created earlier. Use this whenever you want to deploy the latest code committed in Git to Heroku.

During the start of your first build, Initializing repository will be displayed while your app’s repository is created on Heroku. On subsequent builds, Fetching repository will be displayed while your app’s repository is fetched and prepared to accept your push.

Branches pushed to Heroku other than master will be ignored by this command. If you’re working out of another branch locally, you can either merge to master before pushing, or specify that you want to push your local branch to a remote master. To push a branch other than master, use this syntax:

$ git push heroku yourbranch:master

Applications that rely on git submodules are supported, in addition to many other dependency resolution strategies.

git lfs is not supported and may cause pushes to fail.

Build deploy ordering

If multiple parallel builds are started for an app (either by the same user performing multiple pushes, by app collaborators pushing concurrently or because builds are created concurrently with other mechanisms like Build API or GitHub Sync), then the last build to complete will generally be the one that ends up being deployed for the app, even if that build was started before other builds.

Take an example of two builds, A and B: Build A is started, runs slowly and completes in 2 minutes. 30 seconds after build A is started, build B is started and completes in 1 minute. Build B is deployed for the app when it completes. 30 seconds later, build A completes and is deployed for the app. The end result is that build A is deployed on the app, even though build B was started later.

Detach from build process

When deploying code using git push, you can detach from the build process by pressing Ctrl + C. However, your build will continue to process in the background and will create a new release as soon as it finished.

HTTP Git authentication

The Heroku HTTP Git endpoint only accepts API-key based HTTP Basic authentication. A username is not required and any value passed for username is ignored.

You cannot authenticate with the Heroku HTTP Git endpoint using your Heroku username (email) and password. Use an API key as described in this section

If, for any reason, you authenticate to the Git service with incorrect credentials, you’ll get this error:

remote: ! WARNING: remote: ! Do not authenticate with username and password using git. remote: ! Run `heroku login` to update your credentials, then retry the git command. remote: ! See documentation for details: https://devcenter.heroku.com/articles/git\#http-git-authentication

When you do heroku login, the CLI will write an entry for git.heroku.com into your .netrc file (or its Windows equivalent). Since the Git client uses cURL when interacting with HTTP Git remotes, correct authentication will now happen transparently.

If you’re using other Git clients, such as EGit or Tower, configure them to use an empty string for username (or any string you like – it’s ignored) and your account API key for password. The API key is available in the CLI and in Dashboard.

SSH Git transport

The default Git transport configured by the Heroku CLI is HTTP, but SSH transport is also supported. SSH and HTTP transport can be used interchangeably by the same user and by multiple users collaborating on the same app. To have the Heroku CLI configure SSH transport, you can pass a --ssh-git flag to the heroku create, heroku git:remote and heroku git:clone commands.

$ heroku create --ssh-git

To use SSH Git transport, you have to register your SSH key with Heroku. See the Managing SSH Keys article for details.

If you want to always use SSH Git with Heroku on a particular machine, you can add the following global config:

$ git config --global url.ssh://[email protected]/.insteadOf https://git.heroku.com/

HTTP URLs will still be written to .git folders but Git will rewrite, on the fly, all Heroku HTTP Git URLs to use SSH.

To remove this rewrite setting, run:

$ git config --global --remove-section url.ssh://[email protected]/

from "Java The Complete Reference" 9th edition

The For-Each Version of the for Loop

Beginning with JDK 5, a second form of for was defined that implements a “for-each” style loop. As you may know, contemporary language theory has embraced the for-each concept, and it has become a standard feature that programmers have come to expect. A for-each style loop is designed to cycle through a collection of objects, such as an array, in strictly sequential fashion, from start to finish. Unlike some languages, such as C#, that implement a for-each loop by using the keyword foreach, Java adds the for-each capability by enhancing the for statement. The advantage of this approach is that no new keyword is required, and no preexisting code is broken. The for-each style of for is also referred to as the enhanced for loop.

The general form of the for-each version of the for is shown here:

for(type itr-var : collection) statement-block

Here, type specifies the type and itr-var specifies the name of an iteration variable that will receive the elements from a collection, one at a time, from beginning to end. The collection being cycled through is specified by collection. There are various types of collections that can be used with the for, but the only type used in this chapter is the array. (Other types of collections that can be used with the for, such as those defined by the Collections Framework, are discussed later in this book.) With each iteration of the loop, the next element in the collection is retrieved and stored in itr-var. The loop repeats until all elements in the collection have been obtained.

Because the iteration variable receives values from the collection, type must be the same as (or compatible with) the elements stored in the collection. Thus, when iterating over arrays, type must be compatible with the element type of the array.

To understand the motivation behind a for-each style loop, consider the type of for loop that it is designed to replace. The following fragment uses a traditional for loop to compute the sum of the values in an array:

int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; int sum = 0; 

for(int i=0; i \< 10; i++) sum += nums[i];

To compute the sum, each element in nums is read, in order, from start to finish. Thus, the entire array is read in strictly sequential order. This is accomplished by manually indexing the nums array by i, the loop control variable.

The for-each style for automates the preceding loop. Specifically, it eliminates the need to establish a loop counter, specify a starting and ending value, and manually index the array. Instead, it automatically cycles through the entire array, obtaining one element at a time, in

Chapter 5 Control Statements 97

Part I

98 PART I The Java Language sequence, from beginning to end. For example, here is the preceding fragment rewritten

using a for-each version of the for: int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };

 int sum = 0; for(int x: nums) sum += x;

With each pass through the loop, x is automatically given a value equal to the next element in nums. Thus, on the first iteration, x contains 1; on the second iteration, x contains 2; and so on. Not only is the syntax streamlined, but it also prevents boundary errors.

Here is an entire program that demonstrates the for-each version of the for just described:

 // Use a for-each style for loop. class ForEach { 

 public static void main(String args[]) { int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; int sum = 0; 

 // use for-each style for to display and sum the values for(int x : nums) { 

 System.out.println("Value is: " + x);

sum += x; }

 System.out.println("Summation: " + sum); }

}

The output from the program is shown here:

 Value is: 1 Value is: 2 Value is: 3 Value is: 4 Value is: 5 Value is: 6 Value is: 7 Value is: 8 Value is: 9 Value is: 10 Summation: 55

As this output shows, the for-each style for automatically cycles through an array in sequence from the lowest index to the highest.

Although the for-each for loop iterates until all elements in an array have been examined, it is possible to terminate the loop early by using a break statement. For example, this program sums only the first five elements of nums:

// Use break with a for-each style for. class ForEach2 { 

 public static void main(String args[]) { int sum = 0; 

 int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; 

 // use for to display and sum the values for(int x : nums) { 

 System.out.println("Value is: " + x); sum += x; if(x == 5) break; // stop the loop when 5 is obtained

}

 System.out.println("Summation of first 5 elements: " + sum); }

}

As is evident, the for loop stops after the fifth element has been obtained. The break statement can also be used with Java’s other loops, and it is discussed in detail later in this chapter.

There is one important point to understand about the for-each style loop. Its iteration variable is “read-only” as it relates to the underlying array. An assignment to the iteration variable has no effect on the underlying array. In other words, you can’t change the contents of the array by assigning the iteration variable a new value. For example, consider this program:

// The for-each loop is essentially read-only. class NoChange { 

 public static void main(String args[]) { int nums[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; 

 for(int x: nums) { System.out.print(x + " "); x = x \* 10; // no effect on nums

}

 System.out.println(); 

 for(int x : nums) System.out.print(x + " "); 

 System.out.println(); }

}

The first for loop increases the value of the iteration variable by a factor of 10. However, this assignment has no effect on the underlying array nums, as the second for loop illustrates. The output, shown here, proves this point:

 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10

This is what it says in the week02 assignment sheet about stacks:

Create a class encapsulating the notion of a stack. This will work exactly like the [std::stack](http://www.cplusplus.com/reference/stack/stack/) class. Of course, any data-type will need to be supported, so your class will be a template class. It will need to be defined in its own header file (stack.h). The class name must be Stack and will need to support the following operations:

I guess that’s the key. It was DEFINED in the header file…What about the declaration?

How to define a template class in a .h file and implement it in a .cpp file

Febil Chacko Thanikal, 22 Dec 2009 CPOL

4.30 (32 votes)

Rate this:

vote 1 vote 2 vote 3 vote 4 vote 5

This article describdes how to define a template class in a .h file and do its implementation in a .cpp file.

Introduction

This article suggests three methods to implement template classes in a .cpp file.

Background

The common procedure in C++ is to put the class definition in a C++ header file and the implementation in a C++ source file. Then, the source file is made part of the project, meaning it is compiled separately. But when we implement this procedure for template classes, some compilation and linking problems will arise.

Compilation Issue

Here is some sample code:

Hide Shrink Copy Code

// TestTemp.h \#ifndef \_TESTTEMP\_H\_ \#define \_TESTTEMP\_H\_   
template<class T>
class TestTemp   
{
public:
    TestTemp();
    void SetValue( T obj_i );
    T Getalue();

private:

    T m_Obj;
};
\#endif 
// TestTemp.cpp \#include "TestTemp.h" 
TestTemp::TestTemp()
{
}
void TestTemp::SetValue( T obj_i )
{

}
T TestTemp::Getalue()
{
    return m_Obj;
}

If you try to implement the template class like a normal class implementation as shown above, it will generate a set of compilation errors such as:

Hide Copy Code

*: error C2955: 'TestTemp' : use of class template requires template argument list : error C2065: 'T' : undeclared identifier*

Reason

In this case, the compiler doesn't know about the object type. So it will not compile.

Solution

To compile this class without any errors, you need to put the template specific declaration in a .cpp file, as shown below:

Template Class Header File

Hide Copy Code

// TestTemp.h \#ifndef \_TESTTEMP\_H\_ \#define \_TESTTEMP\_H\_  
template<class T>
class TestTemp  
{

public:

    TestTemp();
    void SetValue( T obj_i );
    T Getalue();

private:

    T m_Obj;
};
\#endif

Template Class Source File

Hide Copy Code

// TestTemp.cpp \#include "TestTemp.h"  
template <class T>
TestTemp<T>::TestTemp()
{
}
template <class T>
void TestTemp<T>::SetValue( T obj_i )
{

}
template <class T>
T TestTemp<T>::Getalue()
{
    return m_Obj;
}

Linking Issue

With the above code, after resolving all the compilation errors, you may get some link errors while you create an object of this class in any file other than TestTemp.cpp. Here is some sample code:

Client Source File

Hide Copy Code

// Client.cpp \#include "TestTemp.h" 
    :
    TestTemp<int> TempObj;
    :

Link Error

Hide Copy Code

: error LNK2001: unresolved external symbol "public: __thiscall
TestTemp<int>::TestTemp<int>(void)"
(??0?$TestTemp@H@@QAE@XZ)

Reason

When the compiler encounters a declaration of a TestTemp object of some specific type, e.g., int, it must have access to the template implementation source. Otherwise, it will have no idea how to construct the TestTempmember functions. And, if you have put the implementation in a source (TestTemp.cpp) file and made it a separate part of the project, the compiler will not be able to find it when it is trying to compile the client source file. And, #includeing the header file (TestTemp.h) will not be sufficient at that time. That only tells the compiler how to allocate for the object data and how to build the calls to the member functions, not how to build the member functions. And again, the compiler won't complain. It will assume that these functions are provided elsewhere, and leave it to the linker to find them. So, when it's time to link, you will get "unresolved references" to any of the class member functions that are not defined "inline" in the class definition.

Solution

There are different methods to solve this problem. You can select from any of the methods below depending on which is suitable for your application design.

Mehtod 1

You can create an object of a template class in the same source file where it is implemented (TestTemp.cpp). So, there is no need to link the object creation code with its actual implementation in some other file. This will cause the compiler to compile these particular types so the associated class member functions will be available at link time. Here is the sample code:

Template Class Header File

Hide Copy Code

// TestTemp.h \#ifndef \_TESTTEMP\_H\_ \#define \_TESTTEMP\_H\_ template<class T>
class TestTemp  
{
public:
    TestTemp();
    void SetValue( T obj_i );
    T Getalue();

private:
    T m_Obj;
};
\#endif

Template Class Source File

Hide Copy Code

// TestTemp.cpp \#include "TestTemp.h"  
template <class T>
TestTemp<T>::TestTemp()
{
}

template <class T>
void TestTemp<T>::SetValue( T obj_i )
{
}

template <class T>
T TestTemp<T>::Getalue()
{
    return m_Obj;
}

// No need to call this TemporaryFunction() function, // it's just to avoid link error. void TemporaryFunction ()
{
    TestTemp<int> TempObj;
}

Client Source File

Hide Copy Code

// Client.cpp \#include "TestTemp.h" 
    :
        TestTemp<int> TempObj;
        TempObj.SetValue( 2 );
        int nValue = TempObj.Getalue();
    :

The temporary function in "TestTemp.cpp" will solve the link error. No need to call this function because it's global.

Method 2

You can #include the source file that implements your template class in your client source file. Here is the sample code:

Template Class Header File

Hide Copy Code

// TestTemp.h \#ifndef \_TESTTEMP\_H\_ \#define \_TESTTEMP\_H\_  
template<class T>
class TestTemp  
{
public:
    TestTemp();
    void SetValue( T obj_i );
    T Getalue();
private:
    T m_Obj;
};
\#endif

Template Class Source File

Hide Copy Code

// TestTemp.cpp \#include "TestTemp.h" 
template <class T>
TestTemp<T>::TestTemp()
{
}

template <class T>
void TestTemp<T>::SetValue( T obj_i )
{
}

template <class T>
T TestTemp<T>::Getalue()
{
   return m_Obj;
}

Client Source File

Hide Copy Code

// Client.cpp \#include "TestTemp.h" \#include "TestTemp.cpp"               :
        TestTemp<int> TempObj;
        TempObj.SetValue( 2 );
        int nValue = TempObj.Getalue();
              :

Method 3

You can #include the source file that implements your template class (TestTemp.cpp) in your header file that defines the template class (TestTemp.h), and remove the source file from the project, not from the folder. Here is the sample code:

Template Class Header File

Hide Copy Code

// TestTemp.h \#ifndef \_TESTTEMP\_H\_ \#define \_TESTTEMP\_H\_ template<class T>
class TestTemp  
{
public:
    TestTemp();
    void SetValue( T obj_i );
    T Getalue();
private:
    T m_Obj;
};
\#include "TestTemp.cpp" 
\#endif

Template Class Source File

Hide Copy Code

// TestTemp.cpp \#include "TestTemp.h" 
template <class T>
TestTemp<T>::TestTemp()
{
}
template <class T>
void TestTemp<T>::SetValue( T obj_i )
{
}

template <class T>
T TestTemp<T>::Getalue()
{
    return m_Obj;
}

Client Source File

Hide Copy Code

// Client.cpp \#include "TestTemp.h"                :
    TestTemp<int> TempObj;
    TempObj.SetValue( 2 );
    int nValue = TempObj.Getalue();
               :

An if statement follows this sort of structure:

if (condition) { // executed only if "condition" is true } else if (other condition) { // executed only if "condition" was false and "other condition" is true } else { // executed only if both "condition" and "other condition" were false }

The if portion is the only block that is absolutely mandatory. else if allows you to say "ok, if the previous condition was not true, then if this condition is true...". The else says "if none of the conditions above were true..."

You can have multiple else if blocks, but only one if block and only one (or zero) elseblocks.

Solution:

extends Activity

The function call operator () can be overloaded for objects of class type. When you overload ( ), you are not creating a new way to call a function. Rather, you are creating an operator function that can be passed an arbitrary number of parameters.

Following example explains how a function call operator () can be overloaded.

\#include \<iostream\> using namespace std; class Distance { private: int feet; // 0 to infinite int inches; // 0 to 12 public: // required constructors Distance(){ feet = 0; inches = 0; } Distance(int f, int i){ feet = f; inches = i; } // overload function call Distance operator()(int a, int b, int c) { Distance D; // just put random calculation D.feet = a + c + 10; D.inches = b + c + 100 ; return D; } // method to display distance void displayDistance() { cout \<\< "F: " \<\< feet \<\< " I:" \<\< inches \<\< endl; } }; int main() { Distance D1(11, 10), D2; cout \<\< "First Distance : "; D1.displayDistance(); D2 = D1(10, 10, 10); // invoke operator() cout \<\< "Second Distance :"; D2.displayDistance(); return 0; }

When the above code is compiled and executed, it produces the following result:

First Distance : F: 11 I:10
Second Distance :F: 30 I:120

Hi guys! If you need help, Linux lab assistants are available online. They will contact with you through Google Hangout

You just need to click on this link and put your name on the queue. Although their priorities mostly are for CS124 and CS165 students, they will try their best to help you out

How to remove a directory in my GitHub repository?

[up vote]( "This question shows research effort; it is useful and clear")545[down vote]( "This question does not show any research effort; it is unclear or not useful")favorite

247

I have 2 directories on my GitHub repository. I'd like to delete one of them. How could I do that without deleting and re-creating entire repository?

git github directory delete-file git-bash

](http://stackoverflow.com/users/3540289/eirenaios)

edited Dec 5 at 9:33

[

eirenaios

5,81782971

asked Jun 10 '11 at 23:54

[

](http://stackoverflow.com/users/274117/sahat-yalkabov)

Sahat Yalkabov

8,6482579139

Are there any files in the directories? – Fred Foo Jun 11 '11 at 0:14

2

@Iarsmans: Yes 6 files. Both directories are identical except one is uppercase, another is lowercase. – Sahat Yalkabov Jun 11 '11 at 0:21

[add a comment]( "Use comments to ask for more information or suggest improvements. Avoid answering questions in comments.")

10 Answers

[up vote]( "This answer is useful")1098[down vote]( "This answer is not useful")accepted

Remove directory from git and local

You could checkout 'master' with both directories;

git rm -r one-of-the-directories
git commit -m "Remove duplicated directory"
git push origin <your-git-branch> (typically 'master', but not always)

Remove directory from git but NOT local

As mentioned in the comments, what you usually want to do is remove this directory from git but not delete it entirely from the filesystem (local)

In that case use:

git rm -r --cached myFolder

Ignoring directories in Git repos on Windows

[up vote]( "This question shows research effort; it is useful and clear")511[down vote]( "This question does not show any research effort; it is unclear or not useful")favorite

89

How can I ignore directories or folders in Git using msysgit on Windows?

windows git gitignore msysgit

edited Sep 10 '15 at 11:35

[

](http://stackoverflow.com/users/617450/ripon-al-wasim)

Ripon Al Wasim

17.2k2290123

asked Dec 5 '08 at 12:17

[

](http://stackoverflow.com/users/43603/sf)

sf.

5,52173345

Do you want the cache folder to be excluded from the repository completely, or just its contents? – Gareth Jun 29 '12 at 10:09

I'm guessing that the OP has multiple cache directories, whose contents should be ignored, but wants to make sure that those directories are created for anyone who clones the repository. – Mark Longair Jun 29 '12 at 10:19

@Gareth: since empty folders aren't tracked with git, if the content is ignored, the folder also will be, won't it? – eckes Jun 29 '12 at 10:34

Exactly, hence the index.html files. that way the folders are not empty. – Hailwood Jun 29 '12 at 10:53

1

I only mentioned that because some people use hidden files (commonly .gitkeep) to indicate a directory that should be kept – Gareth Jun 29 '12 at 18:17

[add a comment]( "Use comments to ask for more information or suggest improvements. Avoid answering questions in comments.")

13 Answers

from https://developers.google.com/api-client-library/php/auth/service-accounts

[up vote]( "This answer is useful")724[down vote]( "This answer is not useful")accepted

Create a file named .gitignore in your projects directory. Ignore directories by entering the directory name into the file (with a slash appended):

dir_to_ignore/

More info here.

package com.cs246team01.bugtag;

import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

/**
 * Class:GridObjectHandler
 * This class manages all the gridObjects
 */

public class GridObjectHandler {

    //This holds any object used in game
    private List<GridObject> gridObjects;

    int obstacleWidth = Gdx.graphics.getHeight() / 3;
    int obstacleHeight = Gdx.graphics.getHeight() / 3;

    int bugWidth = Gdx.graphics.getHeight()/16;
    int bugHeight = Gdx.graphics.getHeight()/16;

    int buttonSide = Gdx.graphics.getHeight()/4;
    Bug chaser;
    Bug evader;

    //This will be initialized during the create method
    //of the main game
    public GridObjectHandler() {

        gridObjects = new ArrayList<GridObject>();

        Random rand = new Random();
        boolean isChaser = rand.nextBoolean();

        //Player Textures
        Texture bug1_texture = new Texture("bugs/yellow_idle_large.png");
        Texture bug2_texture = new Texture("bugs/red_idle.png");

        chaser = new Bug(bug1_texture, isChaser, 1);
        evader = new Bug(bug2_texture, false, 2);

        //Obstacle Textures
        Texture obstacleOne   = new Texture("obstacles/Real_Pear.png");
        Texture obstacleTwo   = new Texture("obstacles/Real_Apple.png");
        Texture obstacleThree = new Texture("obstacles/Real_Bread.png");
        Texture obstacleFour  = new Texture("obstacles/Real_Watermelon.png");
        Texture obstacleFive  = new Texture("obstacles/Real_Orange.png");

        //Button textures
        Texture button1 = new Texture("buttons/arrow-left.png");
        Texture button2 = new Texture("buttons/arrow-right.png");
        Texture button3 = new Texture("buttons/arrow-down.png");
        Texture button4 = new Texture("buttons/arrow-up.png");
        Texture button5 = new Texture("buttons/arrow-right.png");
        Texture button6 = new Texture("buttons/arrow-left.png");
        Texture button7 = new Texture("buttons/arrow-up.png");
        Texture button8 = new Texture("buttons/arrow-down.png");

        //Add objects to the array
        gridObjects.add(chaser);
        gridObjects.add(evader);
        gridObjects.add(new Obstacle(obstacleOne));
        gridObjects.add(new Obstacle(obstacleTwo));
        gridObjects.add(new Obstacle(obstacleThree));
        gridObjects.add(new Obstacle(obstacleFour));
        gridObjects.add(new Obstacle(obstacleFive));
        gridObjects.add(new Button(1, button1));
        gridObjects.add(new Button(2, button2));
        gridObjects.add(new Button(3, button3));
        gridObjects.add(new Button(4, button4));
        gridObjects.add(new Button(5,button5));
        gridObjects.add(new Button(6,button6));
        gridObjects.add(new Button(7,button7));
        gridObjects.add(new Button(8,button8));


    }

    //This is the only method we will call in the render method
    public void run() {
        update();

    }

    public Bug getChaser(){
        return chaser;
    }
    public Bug getEvader(){
        return evader;
    }

    //This method checks if we should stop the game
    //It returns a 1 if the chaser wins, 2 if the timer runs out;
    // -1 if game is still going
    public int checkWin(boolean chaserWin, int time) {
        if(time <= 0) {
            return 2;
        }
        else if (chaserWin) {
            return -1;
        }
        else {
            return 0;
        }
    }

    //Checks if screen has been tapped and moves the bug
    /**************************************
     * Update()
     * This method goes through each object in the game and determines which direction
     * they need to move. Bug movement is determined by the ButtonProcessor class.
     *
     *
     */
    private void update() {
        //movement code here...

        for (GridObject g : gridObjects) //todo changes to the bug's position are made here

            if (g instanceof Bug) {

                Bug b = (Bug) g;
                if(b.getPlayerID() == 1)
                    handleMove1(b);
                else
                    handleMove2(b);
            }
    }

    //Keeping it modularized
    public void draw(SpriteBatch batch) {

        for (GridObject g : gridObjects) {
            if(g instanceof Button) {
                batch.draw(g.getTexture(), g.getX(), g.getY(), buttonSide, buttonSide);
            }
            else if (g instanceof Bug)
            {
                batch.draw(g.getTexture(), g.getX(), g.getY(), bugWidth, bugHeight);
            }
            else if(g instanceof Obstacle) {
                batch.draw(g.getTexture(), g.getX(), g.getY(), obstacleWidth, obstacleHeight);
            }
        }
    }

    public void handleMove1(Bug b) {

       if(ButtonProcessor.moveUp1){
           b.moveUp();
           ButtonProcessor.moveUp1 = false;
       }

        if(ButtonProcessor.moveDown1){
            b.moveDown();
            ButtonProcessor.moveDown1 = false;
        }
        if(ButtonProcessor.moveLeft1){
            b.moveLeft();
            ButtonProcessor.moveLeft1 = false;
        }
        if(ButtonProcessor.moveRight1){
            b.moveRight();
            ButtonProcessor.moveRight1 = false;
        }

    }

    //Important Note, Movement is inverted for player two buttons (upButton = moveDown())
    public void handleMove2(Bug b){

        if(ButtonProcessor.moveUp2){
            b.moveDown();
            ButtonProcessor.moveUp2 = false;
        }

        if(ButtonProcessor.moveDown2){
            b.moveUp();
            ButtonProcessor.moveDown2 = false;
        }
        if(ButtonProcessor.moveLeft2){
            b.moveRight();
            ButtonProcessor.moveLeft2 = false;
        }
        if(ButtonProcessor.moveRight2){
            b.moveLeft();
            ButtonProcessor.moveRight2 = false;
        }
    }

    //This takes all of the buttons and places them in a list for the input processor
    public ArrayList<Button> getButtons(){
        ArrayList<Button> buttons = new ArrayList<Button>();
        for (int i = 7; i < gridObjects.size(); i++){
            Button b = (Button) gridObjects.get(i);
            buttons.add(b);
        }

        return buttons;
    }
}

video {
   position: absolute;
   top: 50%;
   left: 50%;
   min-width: 100.5%;
   min-height: 100%;
   width: auto;
   height: auto;
   z-index: 0;
   -webkit-transform: translateX(-50%) translateY(-50%);
   transform: translateX(-50%) translateY(-50%);
   background-size: cover;
   -webkit-transition: 1s opacity;
   transition: 1s opacity;
   overflow: hidden;
   background: no-repeat center center;
   display: inline-block;
   vertical-align: baseline;
   margin: 0;
   padding: 0;
   border: 0;
}

<html lang="en-US">
<head>
    <link rel="stylesheet" href="stylesheet.css">
</head>
<body>
<video muted loop preload="none" autoplay>
    <source src="background.mp4" type="video/mp4">
</video>
</body>
</html>

This is Cheatsheets — a collection of cheatsheets I've written.

Heroku

`create` - Create an app

heroku create sushi

`access` - Collaboration

\# Manage collaborators
  heroku access                     \# List
  heroku access:add [email protected]
  heroku access:remove [email protected]

\# Transfer to another owner
  heroku apps:transfer [email protected]

`logs` - Show logs

heroku logs
heroku logs -t      \# --tail (stream)
heroku logs -s app  \# --source (only on app logs)

`releases`

heroku releases
heroku releases:info v25
heroku rollback

`pg` - Postgresql

# Start a database heroku addons:add heroku-postgresql heroku pg:promote HEROKU\_POSTGRESQL\_PURPLE\_URL \# Enable backups heroku addons:add pgbackups:auto-month

`ps` - Managing processes

heroku ps              \# list
heroku ps:scale web=1  \# spawn more dynos

`restart`

heroku restart

`run` - Running

heroku run bash
heroku run console                  \# Rails console
heroku run rake assets:precompile

`config` - Environment var configuration

heroku config        \# List
heroku config -s     \# List in shell format

heroku config:get KEY

heroku config:set KEY=val
heroku config:set KEY1=val KEY2=val ...

heroku config:unset KEY1

`apps` - Applications

heroku apps                  # list
heroku apps:create [NAME] heroku apps:destroy --app APP heroku apps:info heroku apps:open \# open in browser heroku apps:rename NEWNAME

`maintenance`

heroku maintenance:on
heroku maintenance:off

`domains` - Custom domains

\# Add both!
  heroku domains:add example.com
  heroku domains:add www.example.com

\# Removing:
  heroku domains:clear
  heroku domains:remove example.com

Wildcard domains

heroku addons:add wildcard\_domains \*.yourdomain.com =\> heroku.com

htpasswd (for PHP apps)

Create an .htaccess file in the webroot:

AuthUserFile /app/www/.htpasswd
AuthType Basic
AuthName "Restricted Access"
Require valid-user

Create a .htpasswd file:

$ htpasswd -c .htpasswd [username]

See https://gist.github.com/3316425

References:

Read your scriptures before doing homework.
Say a prayer before attempting project.
LOOK AT THE DEVELOPER'S FORUM BEFORE STARTING PROJECT AND SEE TIPS.
IF AT ANY TIME YOU ARE STUCK, SAY A PRAYER AND ASK THE LORD TO HELP YOU.
ALSO, GET OVER YOURSELF AND LOOK AT THE DEVELOPER’S FORUM.
Become entirely accquainted with the project you’re about to do.

Run the testBed on the .out file found in the week's project and save a PDF or get a hard copy of what it spits out.
Try to make a fairly detailed outline of how you’re going to accomplish what the project is asking from you. This is not a waste of time. What is a waste of time is forming and re-forming entire sections of code and doing trial and error because you don’t know what you’re doing. This will make your use of time on the project SO MUCH MORE effective.
Become familiar with the concepts that the week is asking you to use. Otherwise, you won't even know how to solve the problem the project is asking you to solve. You don't know what you don't know.

Don’t be too reliant on the debugger. Just write good code the first time (see above point).
If at any point you find yourself asking "This is absolutely ridiculous. There is no way it should be this hard," it's probably because you missed a key piece of information or don't understand a concept.
If at any point you find yourself cobbling and hacking together a solution to pass a test on the testBed, you probably didn't read the instructions properly or are not using the resources provided to you in the form of provided files. READ THE COMMENTS in the provided files.
If at any point you find yourself facing problems that nobody ever faced in the Developer's Forum, it's probably because they are doing the project correctly using the provided files, following the instructions, and understanding the concepts the week is trying to teach.
AVOID THE TEMPTATION TO SAY NO CAMMY DO THIS.
AVOID THE ALLURING TEMPTATION TO USE YOUR AMAZING ALGORITHM SKILLS IN LIEU OF UNDERSTANDING KEY CONCEPTS AND READING INSTRUCTIONS. THE SOLUTION IS PROBABLY WAY SIMPLER THAN YOU EVEN REALIZE, BECAUSE YOU HAVEN'T PAID ATTENTION. Don't waste time trying to cobble together a solution that will take forever, make you frustrated, and won't even work in the end (seriously it won't). Just read the Developer's Forum and review the key concepts for the week.

"To support server-to-server interactions, first create a service account for your project in the API Console. If you want to access user data for users in your G Suite domain, then delegate domain-wide access to the service account.

Then, your application prepares to make authorized API calls by using the service account's credentials to request an access token from the OAuth 2.0 auth server.

Finally, your application can use the access token to call Google APIs."

What does this mean?

“...using the service account's credentials to request an access token from the OAuth 2.0 auth server."

And this?

After you have obtained the client email address and private key from the API Console, set the path to these credentials in the GOOGLE_APPLICATION_CREDENTIALS environment variable ( Note: This is not required in the App Engine environment):

Q: What is an environment variable (in PHP)? A: I think its similar to a macro in C++. Here's an example of how to set an environmental variable in PHP:

$_ENV["MYENV"]="new_variable";
$new_variable_var = $_ENV["MYENV"];

// and this is how you use that variable

<?php
echo 'My username is ' .$_ENV["USER"] . '!';
?>

I think my client email address is [email protected] and the key ID is 7f770e696ad92de95d59b619893d921b49905eed.

Alright. So I'm gonna try to make an environment variable called GOOGLE_APPLICATION_CREDENTIALS and set it to the file path in which my service account credentials are stored. What kind of file does it need to be? Can I download it from Google?

Ahah! I found the answer.

export GOOGLE_APPLICATION_CREDENTIALS=<path_to_service_account_file>

Call the useApplicationDefaultCredentials to use your service account credentials to authenticate:

$client = new Google\_Client();
$client-\>useApplicationDefaultCredentials();

If you have delegated domain-wide access to the service account and you want to impersonate a user account, specify the email address of the user account using the method setSubject:

$client-\>setSubject($user\_to\_impersonate);

Use the authorized Google_Client object to call Google APIs in your application.

Ahah! The credentials are only downloaded once, and it's at the creation of the service account. Fortunately I have that file saved in 1Password in the "Google Cloud Platform" login. :)

from https://developers.google.com/identity/protocols/application-default-credentials

PHP

Default credentials are provided by the Google APIs Client Library for PHP, versions 2.0.0 and newer. To use them, call useApplicationDefaultCredentials:

 $client = new Google\_Client();
 $client-\>useApplicationDefaultCredentials();

Then, use the credentials to access an API service as follows:

 $client-\>setScopes(['https://www.googleapis.com/auth/books']);
 $service = new Google\_Service\_Books($client);
 $results = $service-\>volumes-\>listVolumes('Henry David Thoreau’);

To install the Google APIs Client Library for PHP:

https://github.com/google/google-api-php-client

Installation

You can use Composer or simply Download the Release

Composer

The preferred method is via composer. Follow the installation instructions if you do not already have composer installed.

Once composer is installed, execute the following command in your project root to install this library:

composer require google/apiclient:^2.0

Finally, be sure to include the autoloader:

require\_once '/path/to/your-project/vendor/autoload.php';

That probably needs to be in the project file and/or root. So open up a terminal to the pr ject folder, and type

composer require google/apiclient:^2.0

Then, find the path to the autoloader file(s) that it generates, which is mostly likely your ~/project-folder/vender/autoload.php as shown above.

from https://cloud.google.com/docs/authentication#getting_credentials_for_server-centric_flow

Service running on-premises

To run your code outside Google Cloud Platform, such as in your own private datacenter or in another public cloud, you should use Application Default Credentials with explicitly created service accounts:

Use the Google Cloud Platform Console to create a service account, and download its credentials JSON file to your servers. Make sure to keep the file secure.
Set the environment variable GOOGLE_APPLICATION_CREDENTIALS to the path of your downloaded credentials JSON file.

Custom GitHub OAuth tokens

To use code from private GitHub repositories as Composer dependencies, a personal OAuth tokencan be set for authentication. To use such a token on Heroku, follow these steps:

Create a new Token (you do not need to select any scopes, unless you want to pull packages from private repositories, in which case, selecting only the repo scopes will suffice)
Copy the token for use in the next command
$ heroku config:set COMPOSER_GITHUB_OAUTH_TOKEN=YOURTOKEN (replacing “YOURTOKEN” with the actual token from the previous step, of course).

Now, pushes to Heroku will use your token during composer install, and Heroku will confirm its usage:

-----> Installing dependencies...
       NOTICE: Using custom GitHub OAuth token in $COMPOSER_GITHUB_OAUTH_TOKEN

The private repository URL in your composer.json must use the https:// and not the git://protocol for Composer to be able to use the OAuth token for authentication.

For more information, you may also refer to the troubleshooting section in the Composer documentation.

here’s an example from when I ALMOST used one for myself. Yanked it from somewhere online. Not sure where.

##HTML side

<!DOCTYPE html>
<html>
<head>
    <title>Luscious Lobster</title>
    <meta charset="utf-8"/>
    <link rel="stylesheet" type="text/css" href="stylesheet.css">
    <style type="text/css">
        #logo {
            max-width: 18%;
            display: block;
            margin: auto;
            padding:1%;
        }
    </style>
</head>
<body>
<img id="logo" src="lobster_logo.jpg">
<div id="nav">
    <div id="nav_wrapper">
        <ul>
            <li><a href="Week07.html">Home</a></li>
            <li><a href="Shop.html">Shop</a>
                <ul>
                    <li><a href="#">Lobster #1</a></li>
                    <li><a href="#">Lobster #2</a></li>
                    <li><a href="#">Lobster #3</a></li>
                    <li><a href="#">See All</a></li>
                </ul>
            </li>

            <li><a href="#">Cart</a>
            </li>
        </ul>
    </div>
    <!-- Nav wrapper end -->
</div>
<!-- Nav end -->
</body>
</html>

##CSS side

body {
   padding: 0;
   margin: 0;
   font-family: Arial;
   font-size: 17px;
   display: block;
}
 #nav {
   background-color: #141c5b;
   margin-top: 15px 
}
 #nav_wrapper {
   width: 960px;
   margin: 0 auto;
   text-align: center;
}
 #nav ul {
   list-style-type: none;
   padding: 0;
   margin: 0;
   position: relative;
   min-width: 200px;
   display:inline-block;
}
 #nav ul li {
   display: inline-block;
}
 #nav ul li:hover {
   background-color: #1d2e9f;
}
 #nav ul li a, visited {
   color: white;
   display: block;
   padding: 15px;
   text-decoration: none;
}
 #nav ul li:hover ul {
   display: block;
}
 #nav ul ul {
   display: none;
   position: absolute;
   background-color: #1d2e9f;
   border-top: 0;
   margin-left: -5px;
}
 #nav ul ul li {
   display: block;
}
 #nav ul ul li a:hover {
   background-color: #141c5b;
}

A Git workflow looks like this:

A Git repository stores the full history of all of its branches and tags within the .git directory.
The latest stable release is contained within the master branch.
Active feature work is developed in separate branches.
When a feature is finished, the feature branch is merged into master and deleted.

##Git CLI: Handy commands to know

to replace your local git repository with your remote on GitHub:

git reset --hard origin/master. Assuming that "origin/master" is your remote branch you want to reset to.

To merge a different branch into the master branch:

git checkout master git merge branch_name

To see the list of all the commits in the current branch:

git log

To push to two repos at the same time with git push: (below)

git remote set-url --add --push origin [email protected]:namespace/repo.git
git remote set-url --add --push origin [email protected]:namespace/repo.git

##How to connect existing local repo to Github

Initialize the local directory as a Git repository.

git init
Add the files in your new local repository. This stages them for the first commit.

git add . # Adds the files in the local repository and stages them for commit. To unstage a file, use 'git reset HEAD YOUR-FILE'.
Commit the files that you've staged in your local repository.

git commit -m "First commit" # Commits the tracked changes and prepares them to be pushed to a remote repository. To remove this commit and modify the file, use 'git reset --soft HEAD~1' and commit and add the file again.
At the top of your GitHub repository's Quick Setup page, click to copy the remote repository URL.
In Terminal, add the URL for the remote repository where your local repository will be pushed.

git remote add origin remote repository URL # Sets the new remote git remote -v # Verifies the new remote URL
Push the changes in your local repository to GitHub.

git push -u origin master # Pushes the changes in your local repository up to the remote repository you specified as the origin

##How to add Heroku remote to existing local git repository You can verify the remote in your git configuration as well: $ git remote -v heroku https://git.heroku.com/falling-wind-1624.git (fetch) heroku https://git.heroku.com/falling-wind-1624.git (push) You can also take an existing Git repository and add a remote using the git URL provided when you created your app. You may need to do this to associate a Git repository with an existing application. The heroku git:remote command will add this remote for you based on your applications git url. $ heroku git:remote -a falling-wind-1624 Git remote heroku added.

###Instructions V.2

Create a new Heroku project. Don't give it any add-ons.
Clone example project here: git clone https://github.com/kissaten/maven-plugin-war-example
- Alternatively, you may also open IntelliJ and click New Project -> From Version Control -> Github. Then just put in this same repo address above and it'll make it for you.
Add a new servlet by right-clicking on java (under src->main) and selecting New->Servlet.
Change web.xml to reflect the changes. Format it as follows:

<servlet>
  <servlet-name>HelloServlet</servlet-name>
  <servlet-class>HelloServlet</servlet-class>
</servlet>
<servlet-mapping>
  <servlet-name>HelloServlet</servlet-name>
  <url-pattern>/*</url-pattern>
</servlet-mapping>

Then, go to the 'Edit Configurations' for running the app. Click the '+' button to add a new configuration. Make sure it's Maven. Name it "Heroku Deploy". And in the command line box, put heroku:deploy-war. Click 'OK'.
Remove the original git remote from the clone by typing git remote rm origin.
- Then type git remote add origin https://github.com/MrGoodBear/cs313-java.git.
- Then git push --set-upstream origin master
DON'T ADD HEROKU TO GIT. IT'LL SCREW THINGS UP AND MAKE THE HEROKU APP NOT WORK. DON'T PUSH TO HEROKU!
Press the play button to build and deploy your app to Heroku!

Developing a Java EE Application

This feature is supported in the Ultimate edition only.

This tutorial illustrates the Java EE application development workflow.

The application that we will develop will be a minimal one. It'll be a one JSP page Java web application. However, the IntelliJ IDEA features shown here are applicable to Java EE applications of any complexity.

Before you start

Make sure that the following software is installed on your computer:

IntelliJ IDEA ULTIMATE Edition.
Java SE Development Kit (JDK), version 6 or later. Download Oracle JDK.
GlassFish Server, version 3.0.1 or later. Download GlassFish. (You can use any other Java EE-enabled application server. GlassFish is used here just as an example.)
A web browser.

Creating a project

Click Create New Project on the Welcome screen, or select File | New | Project.

The New Project wizard opens. 2. In the left-hand pane, select Java Enterprise. 3. If the JDK that you want to use is already defined in IntelliJ IDEA, select that JDK from the Project SDK list. Otherwise, click New, select JDK, and select the JDK installation folder in the dialog that opens. 4. Specify the application server that you are going to use. (We'll use GlassFish Server.)

If GlassFish is not defined in IntelliJ IDEA yet, click New to the right of the Application Server field and select Glassfish Server.

In the Glassfish Server dialog, specify the GlassFish Server installation directory. 5. Under Additional Libraries and Frameworks, select the Web Application check box.

Click Next. 6. Specify the name for your new project (e.g. JavaEEHelloWorld).

Click Finish and wait while IntelliJ IDEA is creating the project.

Exploring the project structure

When the project is created, you'll see something similar to this in the Project tool window.

JavaEEHelloWorld is a module folder (which in this case coincides with the project folder). The .idea folder and the file JavaEEHelloWorld.iml contain configuration data for your project and module respectively. The folder src is for your Java source code. The folder web is for the web part of your application. At the moment this folder contains the deployment descriptor WEB-INF/web.xml and the file index.jsp intended as a starting page of your application.
External Libraries include your JDK and the JAR files for working with GlassFish.

Developing source code

Our application will be a single JSP page application. Its only function will be to output the text Hello, World!

Open index.jsp for editing: select the file in the Project tool window and press ⌘↓.
Between <body> and </body> type Hello, World!

The code at this step is ready.

Running the application

In the upper-right part of the workspace, click .

IntelliJ IDEA compiles your source code and builds an application artifact.

After that, the Run tool window opens. IntelliJ IDEA starts the server and deploys the artifact onto it.

Finally, your default web browser starts and you see the application output Hello, World! there.

Modifying the code and observing the changes

In index.jsp, change Hello, World! to Hello!.
In the Run tool window, click Update .
In the Update dialog, select Update resources and click OK. (For more information, see Application update options.)
Switch to the web browser and reload the page to see the changes.

See also, Updating Applications on Application Servers.

Exploring a run configuration

When creating the project, we specified GlassFish as an application server. As a result, IntelliJ IDEA created a run configuration for GlassFish.

When we performed the Run command (), we started that run configuration. Now let's take a look at the run configuration and see how its settings map onto the events that we've just observed.

Click the run configuration selector and select Edit Configurations.

The Run/Debug Configurations dialog opens and the settings for the GlassFish run configuration are shown.

The Before launch task list (in the lower part of the dialog) specifies that the application code should be compiled and the corresponding artifact should be built prior to executing the run configuration.

2. Select the Startup/Connection tab to see how the server is started in the run, debug and code coverage modes. 3. Select the Deployment tab to see which artifacts are deployed after the server is started. 4. Go back to the Server tab.

The settings under Open browser specify that after launch (i.e. after the server is started and the artifacts are deployed onto it) the default web browser should start and go to the specified URL (http://localhost:8080/JavaEEHelloWorld_war_exploded).

The settings to the right of On 'Update' action specify that on clicking in the Run tool window the Update dialog should be shown and the Update resources option should be used by default. (The last used update option becomes the default one).

5. Click OK.

Exploring an artifact configuration

When creating the project, we indicated that we were going to develop a web application. As a result, IntelliJ IDEA, among other things, created a configuration for building a web application artifact. Let's have a look at this configuration.

Open the Project Structure dialog: File | Project Structure or ⌘;.
Under Project Settings, select Artifacts.

The available artifact configurations are shown in the pane to the right under and . (There's only one configuration at the moment.)

The artifact settings are shown in the right-hand part of the dialog.

Type. The artifact type is Web Application: Exploded. This is a decompressed web application archive (WAR), a directory structure that is ready for deployment onto a web server.

Output directory. The artifact, when built, is placed into <project_folder>/out/artifacts/JavaEEHelloWorld_war_exploded.

Output Layout. The artifact structure is shown in the left-hand pane of the Output Layout tab.

The <output root> corresponds to the output directory. Other elements have the following meanings:

'JavaEEHelloWorld' compile output represents compiled Java classes whose sources are located in the src directory. These are placed into WEB-INF/classes in the output directory.
'Web' facet resources represent the contents of the web directory.

Packaging the application into a WAR file

When you get to the stage when you are happy with your application, you may want to place it in a WAR (web application archive). To do that, you should create an appropriate artifact configuration and then build the artifact:

Click , point to Web Application: Archive and select For 'JavaEEHelloWorld: war exploded'.

A new artifact configuration is created and its settings are shown in the right-hand part of the dialog.

2. Create a manifest file for your archive: click Create Manifest and agree to the location suggested by IntelliJ IDEA (web/META-INF/MANIFEST.MF). 3. Click OK in the Project Structure dialog. 4. Select Build | Build Artifacts. 5. In the Build Artifact popup, point to JavaEEHelloWorld:war and select Build.

Now if you look at the out/artifacts/JavaEEHelloWorld_war folder, you'll see the archive there.

Deploying an artifact onto a running server

Sometimes you need to deploy your app onto a running server. This section provides a how-to example.

Server run configurations that don't start a server are called remote. Such run configurations can be used, for example, for deploying applications to servers that are already running. (See Local and remote run configurations.)

Let's create a run configuration for deploying our WAR artifact to the running server and see how it works. (By now, the server has been started by the run configuration discussed earlier.)

Click the run configuration selector and select Edit Configurations.
Click , point to GlassFish Server and select Remote.
Change the run configuration name Unnamed to something more sensible (e.g. GlassFishRemote).
Specify the artifact to be deployed to the server: select the Deployment tab, click and select Artifact.

In the dialog that opens, select the WAR artifact.

The result should look similar to this:

5. Click OK in the Run/Debug Configurations dialog.

Now let's see how this run configuration works. 6. Execute the run configuration: click .

The run configuration output is shown in the Run tool window.

After a while, a new tab in your web browser opens, and you see the application output there.

Packaging the application into an EAR: Using Java EE Application support

To package your Java EE application into an EAR, you should:

Create a Java EE deployment descriptor application.xml.
Configure an EAR artifact.
Build that artifact.

As we are about to see, IntelliJ IDEA performs most of these tasks for you as part of its Java EE Application support:

In the Project tool window, right-click your module folder and select Add Framework Support.
In the dialog that opens, select the JavaEE Application check box and click OK.

Note the descriptor file META-INF/application.xml created in your module folder.

3. Open the file in the editor (⌘↓).

At the moment, the file is almost empty. 4. Now let's look at the artifact configurations.

Note that a new configuration appeared, the one for an exploded EAR artifact.

Currently only JavaEE Application facet resources (META-INF/application.xml) are included in the artifact.

5. Let's add a copy of the exploded WAR artifact to the EAR artifact structure. To do that, under Available Elements, expand the Artifacts node and double-click the exploded WAR artifact. Here is the result.

(An alternative way of getting the same result would be | Artifact | JavaEEHelloWorld: war exploded.) 6. Note the message Web facet isn't registered in application.xml. Click Fix. (A bit later, we'll look at the changes made to application.xml by this quick fix.) 7. Create a configuration for an EAR artifact: | JavaEE Application: Archive | For 'JavaEEHelloWorld:ear exploded'. 8. To create a manifest file, click Create Manifest and agree to the default file location (<project_folder>/META-INF/MANIFEST.MF). 9. Click OK in the Project Structure dialog.

See that your application.xml has changed. This is the result of applying the quick fix.

Let's now create a run configuration for building and deploying the EAR artifact. 10. Click the run configuration selector and select Edit Configurations. Then, in the Run/Debug Configurations dialog, select | GlassFish Server | Remote. 11. Specify a descriptive name for your run configuration, e.g. GlassFishRemoteEAR. 12. Include the EAR artifact in the deployment list: switch onto the Deployment tab and select | Artifact | JavaEEHelloWorld:ear.

Note that the Build 'JavaEEHelloWorld:ear' artifact task is included in the Before launch task list automatically.

13. Switch to the Server tab and check the URL in the Open browser section. The part that follows http://localhost:8080/should correspond to the <context-root> element in your application.xml. 14. Click OK in the Run/Debug Configurations dialog. 15. Execute the run configuration ().

As before, another tab opens in the Run tool window showing the run configuration output.

Then, the application output is shown in the browser.

Now if you look at the Project tool window, you'll see your archive in the out/artifacts/JavaEEHelloWorld_ear folder.

Looking at other features (tool windows and facets)

As part of its Web Application and Java EE Application support, IntelliJ IDEA:

Made the Web and JavaEE:App tool windows available.
Created the Web and Java EE Application facets.

Tool windows. To open the tool windows, you can, for example, select View | Tool Windows | Web or View | Tool Windows | JavaEE:App.

Very briefly, the Web and JavaEE:App tool windows provide the functions similar to those of the Project tool window but only for your Web and Java EE Application facet resources respectively. For more info, see:

Facets. To view or edit the facet settings, open the Project Structure dialog, select Modules, and then select Web or javaEEApplication under the module node. For more info, see:

Meet IntelliJ IDEA JavaFX

List of core configure options ¶

http://php.net/manual/en/configure.about.php

Below is a partial list of configure options used by the PHP configurescripts when compiling in Unix-like environments. Most configure options are listed in their appropriate locations on the extension reference pages and not here. For a complete up-to-date list of configure options, run ./configure --help in your PHP source directory after running autoconf(see also the Installation chapter). You may also be interested in reading the » GNU configure documentation for information on additional configure options such as --prefix=PREFIX.

Note:

These are only used at compile time. If you want to alter PHP's runtime configuration, please see the chapter on Runtime Configuration.

Make a new database through the database tab on the upper right of the IDE.
Choose PostgreSQL.
if you see this error when you try to run a PHP file referencing the file: "Warning: pg\_query(): Query failed: ERROR: relation "questions" does not exist”, it means that the table or element or whatever hasn’t been initialized yet. When it’s initialized, the table or column will show up under the Postgres database in the ‘Database’ tab on the right.
The SQL statements you made are called a ‘script’, and they need to be executed in order to be initialized and created in the database and referenced from PHP.
To do this, click ‘Execute’ (see screenshot!) or that green play button in the immediate upper left of that editor screen. Alternatively, you can select each statement separately and press ‘⌘⏎’ to have just that statement executed and built.

P.s. this link is really helpful https://www.jetbrains.com/help/idea/2016.1/running-sql-script-files.html

I noticed that when I try to go straight to a .jsp or .html file in the Run Configurations, it wouldn’t work if there was ANY sort of servlet mapping. Instead, it would just show servlet stuff. It was pretty frustrating.

Hmm…are servlets expected to run everything? direct to every web page from the start? Hmm…...

Differences between a class and a struct in C++ are that structs have default publicmembers and bases and classes have default private members and bases. Both classes and structs can have a mixture of public and private members, can use inheritance and can have member functions. Classes create a namespace that also encapsulates the functions for manipulating its data elements. Classes may not be used when interfacing with C, because C does not have a concept of classes.

I would recommend using structs as plain-old-data structures without any class-like features, and using classes as aggregate data structures with private data and member functions.

###Another answer:

As everyone else notes there are really only two actual language differences:

struct defaults to public access and class defaults to private access.
When inheriting, struct defaults to public inheritance and class defaults to privateinheritance. (Ironically, as with so many things in C++, the default is backwards: publicinheritance is by far the more common choice, but people rarely declare structs just to save on typing the "public" keyword.

But the real difference in practice is between a class/struct that declares a constructor/destructor and one that doesn't. There are certain guarantees to a "plain-old-data" POD type, that no longer apply once you take over the class's construction. To keep this distinction clear, many people deliberately only use structs for POD types, and, if they are going to add any methods at all, use classes. The difference between the two fragments below is otherwise meaningless:

#From email from Bro. Bradshaw

Things to Check

Did you use the HTML5 doctype?
Did you exclude a base tag?
Did you use only relative links/urls?
Did you set your permissions correctly?
Did you check your assignment over an SSH tunnel?

SSH into the Linux Lab

Read "Welcome - Linux Lab Setup” under "Welcome" which has information about how to ssh into the server. If you have not logged into the Linux Lab before, your username is the same as used for www.byui.edu, but all lowercase. Your password may be: the default password Temple4dpc, the first eight characters of your email address, or the password you used last semester.

To change passwords on the Linux Lab Servers

In a terminal/console window, type in the command: yppasswd
Enter the old and new passwords; nothing will display as you type, not even ***
Do not use the numbers on the number keypad to enter numbers
Please use a secure password; the first 8 characters should not be a dictionary word

Create Default Directories and Files Once you can successfully log into the server you will want to read "Week 02 - Ponder : Web Page” which has information about how to set up your directory.

Permissions 711 - root directory (drwx--x--x) 755 - all directories under root (drwxr-xr-x) 644 - all files (-rw-r--r--)

##Use chmod -R to change all files and folders at once! You need to be outside of the directory, and use it right on the directory. The -R makes it recursive.

If you are familiar with Linux and bash you should be able to follow the instructions easily. But for those who are new, here are the steps I took while following the instructions.

#ssh into the server (replace allredjo) ssh [email protected] -p 215

#make sure you are in the root directory pwd #set the permissions on the root directory chmod 711 . (USE THAT PERIOD AT THE END RIGHT THERE) #create the public_html directory mkdir public_html #set the permissions on this directory chmod 755 public_html #change to the public_html directory cd public_html

#create index.html using nano nano index.html #write the html into index.html #edit file then save and close (cmd-o and cmd-x)

#OR create index.html using vi vi index.html #enter text mode by pressing i #write the html into index.html #exit text mode by clicking esc #save the file and exit vi by pressing ZZ

#OR create index.html using some other text editor such as emacs

#OR create the index.html file on your computer and upload it via SFTP

#set permissions on the file chmod 644 index.html #check the permissions to make sure they are correct ls -al #make all the week directories mkdir week{02..13} #set the permissions on all the week directories chmod 755 $(find . -type d) #copy index.html into all the directories echo week* | xargs -n 1 cp index.html #set the permission on all the files just copied find . -type f -print | xargs chmod 644

Create your Home Page

Now follow the instructions to modify index.html to have a link to the index.html file in each folder. I recommend using an SSH FTP tool, such as Cyberduck on the Mac, to SFTP into your directory so you can create your HTML files on your desktop and then SFTP them to the server. You will need to set the permissions on your files when you are done.

Note 0: The work this week, and throughout the remainder of the semester, is mean to be done by hand. Do NOT use third party libraries like jQuery, bootstrap, foundation, etc.

Note 1: Please use HTML5 syntax instead of the older HTML4 or XHTML syntax. The main thing you need to do is use the HTML5 doctype <!DOCTYPE html> instead of the older XHTML doctype <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN” "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"\>

Note 2: Since I am not on campus I have to create an SSH tunnel into the network to grade your assignments. Using a base tag makes it so that I cannot grade your assignments. Do NOT use a base tag (even thought the instructions specify that you should).

Note 3: Also, since I am grading over an SSH Tunnel you MUST NOT use absolute links since I will not be able to grade your assignment if you do. This applies not just to this assignment, but to every assignment this semester. Do NOT use absolute links such as <a href=“http://157.201.194.254/~bradshawr/week02/index.html”\>Week 02</a> Instead use relative links such as <a href=“week02/index.html”>Week 02</a> If you need to create a relative link to a file higher up than your current file you should use “../“ for every level you need to go up. For instance, if you are in the week02/index.html file and you want to create a link to your home page in the folder above week02 your relative url would look like <a href=“../index.html”>Home Page</a>. If you wanted to go up two levels you would use "../../“.

Note 4: Do NOT use spaces in any file or directory names. Again, doing so makes grading very difficult for me.

Note 5: The instructions state that you must validate the page. Due to the nature of HTML5, there is not a good HTML5 validator. So, you do not have to validate your page. If you want to try to find an online HTML5 validator you are welcome to do so, but you do not need to put a logo on the page.

Be sure you follow the instructions. When I grade your home page I will check to see:

Does each link work?
Are the links centered?
Is there a title?
Is there heading text?
Are all links present?
Are the links in a <ul><li> structure?
Are the links relative instead of absolute?
Is there NO base tag?
Are you using the HTML5 doctype?

Setup SSH Tunnel

Next you will want to try viewing your index.html file in a browser and make sure you can click on all the links to make sure everything is set up correctly.

If you are on the BYU-I network you can just go to http://157.201.194.254/~bradshawr/index.html (replace bradshawr).

If you are not on-campus using the BYU-I network then you need to create a secure connection between your local computer and the Linux Lab so that requests from your browser will go thru. We do this using SSH Tunneling (also called SSH Port Forwarding).

Even if you do have access to the BYU-I network I would still recommend that you learn how to set up an SSH tunnel off the BYU-I network. You will want to make sure your assignments work correctly when accessed via an SSH tunnel since that is how I will be grading them.

The following information is specific to Linux, but it has some good general information about SSH Tunnels (port forwarding) if you are not familiar with the concept. https://help.ubuntu.com/community/SSH/OpenSSH/PortForwarding

Mac/OSX, Linux, or any other Unix-variant Open your command line interface (Terminal) and enter (replacing bradshawr with your ID): sudo ssh -L 80:157.201.194.254:80 -p 215 -l bradshawr -N 157.201.194.202 You will need to enter your desktop password and then your Linux Lab password. The ssh tunnel should be established if you no longer have a command prompt and there are no error messages. You might see a gray rectangle. Now you can go to your browser and enter the URL http://localhost/~bradshawr/index.html (replacing bradshawr with your ID).

Windows Download plink.exe from http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html Move plink.exe from where you downloaded it to C:\Windows (or any other folder that is in your PATH). Open your Command Prompt window and enter (replacing bradshawr with your ID): plink -ssh -L 80:157.201.194.254:80 -P 215 -l bradshawr -N 157.201.194.202 You will need to enter your Linux Lab password. The ssh tunnel should be established if you no longer have a command prompt and there are no error messages. You might see a blinking underscore. Now you can go to your browser and enter the URL http://localhost/~bradshawr/index.html (replacing bradshawr with your ID).

Notes:

This needs to be entered on your local desktop machine. Sometimes students will SSH into the Linux Lab and then try to create the SSH Tunnel there. That will not work.
If you are having trouble, it is possible that port 80 is already in use on your computer. If you run into any trouble establishing a connection try replacing 80:157.201.194.254:80 with 8080:157.201.194.254:80 Then in your browser enter the URL http://localhost:8080/~bradshawr/index.html (replacing bradshawr with your ID).
If you are still having trouble, it is possible that port 8080 is already in use on your computer. You can use any unused port number between 1025 and 49150. For example, you could use 7685:157.201.194.254:80 Then in your browser enter the URL http://localhost:7685/~bradshawr/index.html (replacing bradshawr with your ID).
If you are still having trouble, it is possible that the 157.201.194.202 server is down. Try using 157.201.194.203 or 157.201.194.204.
If you are still having trouble, there may be a VPN/firewall/other issue that is preventing the connection. Try establishing the tunnel on another network to see if it works there.
If you are still having trouble, try SSHing into the Linux Lab to make sure it is online. If the Linux Lab is down for maintenance then you will not be able to establish an SSH Tunnel.
If you are still having trouble please contact the instructor.

If you are on Windows and you would like to use PuTTY to setup an SSH Tunnel there are some instructions here: http://emp.byui.edu/ercanbracks/cs213/Tunneling.htm

Note 0: If you are using Windows and you already have PuTTY installed, you might need to update to the latest version.

Note 1: If you are using Windows, make sure IIS is not running since it uses port 80 by default. IIS runs automatically on Windows 10 and perhaps on earlier versions of Windows as well. Or you could leave IIS running and use a different port in PuTTY such as 7007.

Note 2: If it still doesn’t work then even if you don’t think IIS is running on your machine try using a different port such as 7007.

Beginner’s Guide to Java eNum – Why and for What should I use Enum? Java Enum Examples

Last Updated on November 16th, 2016 by App Shah

Enums are lists of constants. When you need a predefined list of values which do represent some kind of numeric or textual data, you should use an enum. For instance, in a chess game you could represent the different types of pieces as an enum:

1

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enum ChessPiece {

PAWN,

ROOK,

KNIGHT,

BISHOP,

QUEEN,

KING;

}

You should always use enums when a variable (especially a method parameter) can only take one out of a small set of possible values. Examples would be things like type constants (contract status: “permanent”, “temp”, “apprentice”), or flags (“execute now”, “defer execution”).

If you use enums instead of integers (or String codes), you increase compile-time checking and avoid errors from passing in invalid constants, and you document which values are legal to use.

Java - Interfaces

An interface is a reference type in Java. It is similar to class. It is a collection of abstract methods. A class implements an interface, thereby inheriting the abstract methods of the interface.

Along with abstract methods, an interface may also contain constants, default methods, static methods, and nested types. Method bodies exist only for default methods and static methods.

Writing an interface is similar to writing a class. But a class describes the attributes and behaviors of an object. And an interface contains behaviors that a class implements.

Unless the class that implements the interface is abstract, all the methods of the interface need to be defined in the class.

An interface is similar to a class in the following ways −

An interface can contain any number of methods.
An interface is written in a file with a .java extension, with the name of the interface matching the name of the file.
The byte code of an interface appears in a .class file.
Interfaces appear in packages, and their corresponding bytecode file must be in a directory structure that matches the package name.

However, an interface is different from a class in several ways, including −

You cannot instantiate an interface.
An interface does not contain any constructors.
All of the methods in an interface are abstract.
An interface cannot contain instance fields. The only fields that can appear in an interface must be declared both static and final.
An interface is not extended by a class; it is implemented by a class.
An interface can extend multiple interfaces.

Declaring Interfaces

The interface keyword is used to declare an interface. Here is a simple example to declare an interface −

Example

Following is an example of an interface −

/\* File name : NameOfInterface.java \*/ import java.lang.\*; // Any number of import statements public interface NameOfInterface { // Any number of final, static fields // Any number of abstract method declarations\\ }

Interfaces have the following properties −

An interface is implicitly abstract. You do not need to use the abstractkeyword while declaring an interface.
Each method in an interface is also implicitly abstract, so the abstract keyword is not needed.
Methods in an interface are implicitly public.

Example

/\* File name : Animal.java \*/ interface Animal { public void eat(); public void travel(); }

Implementing Interfaces

When a class implements an interface, you can think of the class as signing a contract, agreeing to perform the specific behaviors of the interface. If a class does not perform all the behaviors of the interface, the class must declare itself as abstract.

A class uses the implements keyword to implement an interface. The implements keyword appears in the class declaration following the extends portion of the declaration.

Example

/\* File name : MammalInt.java \*/ public class MammalInt implements Animal { public void eat() { System.out.println("Mammal eats"); } public void travel() { System.out.println("Mammal travels"); } public int noOfLegs() { return 0; } public static void main(String args[]) { MammalInt m = new MammalInt(); m.eat(); m.travel(); } }

This will produce the following result −

Output

Mammal eats
Mammal travels

When overriding methods defined in interfaces, there are several rules to be followed −

Checked exceptions should not be declared on implementation methods other than the ones declared by the interface method or subclasses of those declared by the interface method.
The signature of the interface method and the same return type or subtype should be maintained when overriding the methods.
An implementation class itself can be abstract and if so, interface methods need not be implemented.

When implementation interfaces, there are several rules −

A class can implement more than one interface at a time.
A class can extend only one class, but implement many interfaces.
An interface can extend another interface, in a similar way as a class can extend another class.

Extending Interfaces

An interface can extend another interface in the same way that a class can extend another class. The extends keyword is used to extend an interface, and the child interface inherits the methods of the parent interface.

The following Sports interface is extended by Hockey and Football interfaces.

Example

// Filename: Sports.java public interface Sports { public void setHomeTeam(String name); public void setVisitingTeam(String name); } // Filename: Football.java public interface Football extends Sports { public void homeTeamScored(int points); public void visitingTeamScored(int points); public void endOfQuarter(int quarter); } // Filename: Hockey.java public interface Hockey extends Sports { public void homeGoalScored(); public void visitingGoalScored(); public void endOfPeriod(int period); public void overtimePeriod(int ot); }

The Hockey interface has four methods, but it inherits two from Sports; thus, a class that implements Hockey needs to implement all six methods. Similarly, a class that implements Football needs to define the three methods from Football and the two methods from Sports.

Extending Multiple Interfaces

A Java class can only extend one parent class. Multiple inheritance is not allowed. Interfaces are not classes, however, and an interface can extend more than one parent interface.

The extends keyword is used once, and the parent interfaces are declared in a comma-separated list.

For example, if the Hockey interface extended both Sports and Event, it would be declared as −

Example

public interface Hockey extends Sports, Event

Tagging Interfaces

The most common use of extending interfaces occurs when the parent interface does not contain any methods. For example, the MouseListener interface in the java.awt.event package extended java.util.EventListener, which is defined as −

Example

package java.util; public interface EventListener {}

An interface with no methods in it is referred to as a tagging interface. There are two basic design purposes of tagging interfaces −

Creates a common parent − As with the EventListener interface, which is extended by dozens of other interfaces in the Java API, you can use a tagging interface to create a common parent among a group of interfaces. For example, when an interface extends EventListener, the JVM knows that this particular interface is going to be used in an event delegation scenario.

Adds a data type to a class − This situation is where the term, tagging comes from. A class that implements a tagging interface does not need to define any methods (since the interface does not have any), but the class becomes an interface type through polymorphism.

if installed by homebrew, via brew install glassfish

/usr/local/Cellar/glassfish/4.1.1/libexec

Enter a filename in the File Open dialog

[up vote]( "This question shows research effort; it is useful and clear")45[down vote]( "This question does not show any research effort; it is unclear or not useful")favorite

14

Can I enter a path to a file and its name instead of selecting a file in Mac OS X file dialog?

I tried just typing into an open dialog but it will just try to "Go to a folder", it won't accept a full path.

I'm on Mac OS X Lion

macos hidden-file

edited Oct 5 '11 at 20:25

[

](http://apple.stackexchange.com/users/292/ian-c)

Ian C.♦

29.8k19114182

asked Oct 5 '11 at 20:07

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valya

7482810

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3 Answers

design-patterns model-view-controller user-interface mvp glossary

[up vote]( "This answer is useful")36[down vote]( "This answer is not useful")accepted

Since it looks like you're just trying to open a hidden file, in the open dialog press command+shift+. and the hidden files will appear.

package com.cs246team01.bugtag;

import com.badlogic.gdx.Game;
import com.badlogic.gdx.Gdx;
import com.badlogic.gdx.Preferences;
import com.badlogic.gdx.graphics.Color;
import com.badlogic.gdx.graphics.GL20;
import com.badlogic.gdx.graphics.Texture;
import com.badlogic.gdx.graphics.g2d.SpriteBatch;
import com.badlogic.gdx.graphics.g2d.freetype.FreeTypeFontGenerator;
import com.badlogic.gdx.graphics.g2d.freetype.FreeTypeFontGenerator.FreeTypeFontParameter;
import com.badlogic.gdx.graphics.g2d.BitmapFont;

import static com.cs246team01.bugtag.GridObject.TAG;

public class MainGame extends Game{

    //Start screen - can possibly remove this. But buttons show up
    private SpriteBatch welcome;

    /*
    * gameState tracks the state of the game.
    * 0 is start screen, 1 is in gameplay, and 2 is pause, 3 is game over.
    * When various screens are used. This is important to keep track of
    * how to handle touch inputs
    */
    private static int GAME_NOT_STARTED = 0;
    private static int GAME_STARTED = 1;
    private static int GAME_PAUSED = 2;
    private static int GAME_OVER = 3;
    private static int GAME_WARM_UP = 4;
    private int gameState = GAME_NOT_STARTED;

    //Game
    private SpriteBatch batch;
    private GridObjectHandler bugGame;
    private ButtonProcessor buttonProcessor;
    private Win hasWinner;
    private int winner = 0;

    //Timer
	private GameTime timer;
	private float totalTime;

    //Font
	private FreeTypeFontGenerator fontFT;
	private FreeTypeFontParameter parameter;
    private BitmapFont font;

    //Digital Font
    private FreeTypeFontGenerator digitalFontFT;
    private FreeTypeFontParameter digitalParameter;
    private BitmapFont digitalFont;

	//Test Preferences
	private int numMoves = 0;

	//Use this for tagging bugs
	private static final String TAG = "DebugTagger";

	@Override
	public void create () {
		Preferences numMovesPrefs = Gdx.app.getPreferences("MOVES");
		numMoves = numMovesPrefs.getInteger("moves", 0);

		//Debugging only - remove
		Gdx.app.log(TAG,"The number of moves are " + numMoves);

		//Since this is a constant (or is it?)
		//we can just assign a hardcoded value
		totalTime = 63;
		timer = new GameTime(totalTime);

		//Font is comic sans and font size is 50 colored red
		fontFT = new FreeTypeFontGenerator(Gdx.files.internal("fonts/chewy.ttf"));
		parameter = new FreeTypeFontParameter();
		parameter.size = 50;
        parameter.borderColor = Color.BLACK;
        parameter.borderStraight = true;
        parameter.borderWidth = 2f;
		font = fontFT.generateFont(parameter);
		font.setColor(Color.RED);

        //Digital font is digital dream
        digitalFontFT = new FreeTypeFontGenerator(Gdx.files.internal("fonts/digital-dream-skew-narrow.ttf"));
        digitalParameter = new FreeTypeFontParameter();
        digitalParameter.size = 40;
        digitalParameter.borderColor = Color.BLACK;
        digitalParameter.borderStraight = true;
        digitalParameter.borderWidth = 1f;
        digitalFont = digitalFontFT.generateFont(digitalParameter);
        digitalFont.setColor(Color.RED);

		batch = new SpriteBatch();
        welcome = new SpriteBatch();

		bugGame = new GridObjectHandler();

		buttonProcessor = new ButtonProcessor(bugGame.getButtons(), gameState);
        Gdx.input.setInputProcessor(buttonProcessor);
	}

	@Override
	public void render () {
		super.render();
		Gdx.gl.glClearColor(1, 1, 1, 1);
		Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);

        gameState = buttonProcessor.getGameState();

        if(gameState == GAME_NOT_STARTED)
        {
            //TODO Start button? And background graphics
            welcome.begin();

            displayMessage();

            welcome.end();
        }else if(gameState == GAME_WARM_UP)
        {
            //If game is restarted, the timer will be less
            // than 0 and must be set to 63 again.
            if(timer.getTimeRemaining() <= 0){
                timer.setTimeRemaining(63);
            }

            batch.begin();

            bugGame.draw(batch);

            displayTime();

            displayMessage();

            timer.run();
            if(timer.getTimeRemaining() < 60){
                buttonProcessor.setGameState(GAME_STARTED);
            }

            batch.end();
        }
        else if(gameState == GAME_STARTED)
        {
            batch.begin();

            //This is where we run our game //todo this is where the game runs
            bugGame.run();
            hasWinner.checkWin(bugGame.getChaser(),bugGame.getEvader());

            bugGame.draw(batch);

            //moved timer code into this method
            displayTime();

            batch.end();

            //update timer value
            timer.run();

            if(!(timer.getTimeRemaining() > 0)){
                buttonProcessor.setGameState(GAME_OVER);
            }
            //Gdx.app.log(TAG, "Time Remaining is " + timer.getTimeRemaining());
        }
        else if (gameState == GAME_PAUSED)
        {
            batch.begin();

            bugGame.draw(batch);

            displayTime();

            displayMessage();

            batch.end();
        }
        else if (gameState == GAME_OVER)
        {
            batch.begin();

            bugGame.draw(batch);

            displayTime();

            displayMessage();

            //Set winner variable too. The first frame
            // won't have the result but that should be fine

            //Do something with SharedPrefs,
            //like setting the high score, etc.

            batch.end();
        }

	}
	
	@Override
	public void dispose () {
        welcome.dispose();
		batch.dispose();
		font.dispose();
        digitalFont.dispose();
    }

	public void displayTime(){
		//Display timer
		if(timer.getTimeRemaining() >= 60) {
			digitalFont.draw(batch, "0:60",
					Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 12),
					Gdx.graphics.getWidth() / 2);
		} else if(timer.getTimeRemaining() >= 10) {
            digitalFont.draw(batch, "0:" + timer.getTimeRemaining(),
                    Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 12),
                    Gdx.graphics.getWidth() / 2);
        } else if (timer.getTimeRemaining() < 10 && timer.getTimeRemaining() > 0) {
            digitalFont.draw(batch, "0:0" + timer.getTimeRemaining(),
					Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 12),
					Gdx.graphics.getWidth() / 2);
		} else {
            digitalFont.draw(batch, "0:00",
					Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 12),
					Gdx.graphics.getWidth() / 2);
			font.draw(batch, "TIME UP",
					Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 10),
					Gdx.graphics.getWidth() / 3);
        }

	}

	public void displayMessage(){
        if(gameState == GAME_NOT_STARTED) {
            font.draw(welcome, "BUGTAG!",
                    Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 5) ,
                    Gdx.graphics.getWidth() / 2 );
            font.draw(welcome, "Press anywhere to start!",
                    Gdx.graphics.getHeight() / 2 ,
                    Gdx.graphics.getWidth() / 4 );

        } else if(gameState == GAME_WARM_UP)
        {
            font.draw(batch, "Game starts in",
                    Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 5) ,
                    Gdx.graphics.getWidth() / 3 );
            font.draw(batch, (timer.getTimeRemaining() - 60) + "...",
                    Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 12) ,
                    Gdx.graphics.getWidth() / 4 );
        }
        else if (gameState == GAME_PAUSED) {
            font.draw(batch, "GAME PAUSED!",
                    Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 5) ,
                    Gdx.graphics.getWidth() / 3 );
            font.draw(batch, "Press anywhere to resume!",
                    Gdx.graphics.getHeight() / 3 ,
                    Gdx.graphics.getWidth() / 4 );
        } else if (gameState == GAME_OVER) {
            font.draw(batch, "GAME OVER!",
                    Gdx.graphics.getHeight() - (Gdx.graphics.getWidth() / 5) ,
                    Gdx.graphics.getWidth() / 4 );
            if(winner == 1) {
                font.draw(batch, "Player 1 won the game!",
                        Gdx.graphics.getHeight() / 2 ,
                        Gdx.graphics.getWidth() / 5 );
            } else if (winner == 2)
            {
                font.draw(batch, "Player 2 won the game!",
                        Gdx.graphics.getHeight() / 2 ,
                        Gdx.graphics.getWidth() / 5 );
            }
            font.draw(batch, "Press anywhere to restart!",
                    Gdx.graphics.getHeight() / 3 ,
                    Gdx.graphics.getWidth() / 6 );
        }
    }

}

What are MVP and MVC and what is the difference?

Ask Question

[up vote]( "This question shows research effort; it is useful and clear")1529[down vote]( "This question does not show any research effort; it is unclear or not useful")favorite

1001

When looking beyond the RAD (drag-drop and configure) way of building user interfaces that many tools encourage you are likely to come across three design patterns called Model-View-Controller, Model-View-Presenter and Model-View-ViewModel. My question has three parts to it:

What issues do these patterns address?
How are they similar?
How are they different?

](http://stackoverflow.com/users/63550/peter-mortensen)

edited May 4 '15 at 3:26

[

Peter Mortensen

10.9k1575109

asked Aug 5 '08 at 10:06

[

](http://stackoverflow.com/users/358/mike-minutillo)

Mike Minutillo

18.6k123841

1

mvc.givan.se/#mvp – givanse Dec 11 '16 at 16:51

[add a comment]( "Use comments to ask for more information or suggest improvements. Avoid answering questions in comments.")

20 Answers

[up vote]( "This answer is useful")1561[down vote]( "This answer is not useful")accepted

Model-View-Presenter

In MVP, the Presenter contains the UI business logic for the View. All invocations from the View delegate directly to Presenter. The Presenter is also decoupled directly from the View and talks to it through an interface. This is to allow mocking of the View in a unit test. One common attribute of MVP is that there has to be a lot of two-way dispatching. For example, when someone clicks the "Save" button, the event handler delegates to the Presenter's "OnSave" method. Once the save is completed, the Presenter will then call back the View through its interface so that the View can display that the save has completed.

MVP tends to be a very natural pattern for achieving separated presentation in Web Forms. The reason is that the View is always created first by the ASP.NET runtime. You can find out more about both variants.

Two primary variations

Passive View: The View is as dumb as possible and contains almost zero logic. The Presenter is a middle man that talks to the View and the Model. The View and Model are completely shielded from one another. The Model may raise events, but the Presenter subscribes to them for updating the View. In Passive View there is no direct data binding, instead the View exposes setter properties which the Presenter uses to set the data. All state is managed in the Presenter and not the View.

Pro: maximum testability surface; clean separation of the View and Model
Con: more work (for example all the setter properties) as you are doing all the data binding yourself.

Supervising Controller: The Presenter handles user gestures. The View binds to the Model directly through data binding. In this case it's the Presenter's job to pass off the Model to the View so that it can bind to it. The Presenter will also contain logic for gestures like pressing a button, navigation, etc.

Pro: by leveraging databinding the amount of code is reduced.
Con: there's less testable surface (because of data binding), and there's less encapsulation in the View since it talks directly to the Model.

Model-View-Controller

In the MVC, the Controller is responsible for determining which View is displayed in response to any action including when the application loads. This differs from MVP where actions route through the View to the Presenter. In MVC, every action in the View correlates with a call to a Controller along with an action. In the web each action involves a call to a URL on the other side of which there is a Controller who responds. Once that Controller has completed its processing, it will return the correct View. The sequence continues in that manner throughout the life of the application:

    Action in the View
        -> Call to Controller
        -> Controller Logic
        -> Controller returns the View.

One other big difference about MVC is that the View does not directly bind to the Model. The view simply renders, and is completely stateless. In implementations of MVC the View usually will not have any logic in the code behind. This is contrary to MVP where it is absolutely necessary because, if the View does not delegate to the Presenter, it will never get called.

Presentation Model

One other pattern to look at is the Presentation Model pattern. In this pattern there is no Presenter. Instead the View binds directly to a Presentation Model. The Presentation Model is a Model crafted specifically for the View. This means this Model can expose properties that one would never put on a domain model as it would be a violation of separation-of-concerns. In this case, the Presentation Model binds to the domain model, and may subscribe to events coming from that Model. The View then subscribes to events coming from the Presentation Model and updates itself accordingly. The Presentation Model can expose commands which the view uses for invoking actions. The advantage of this approach is that you can essentially remove the code-behind altogether as the PM completely encapsulates all of the behaviour for the view. This pattern is a very strong candidate for use in WPF applications and is also called Model-View-ViewModel.

There is a MSDN article about the Presentation Model and a section in the Composite Application Guidance for WPF (former Prism) about Separated Presentation Patterns

10 revs, 8 users 58% Glenn Block

edited Jan 26 at 15:49

community wiki

1

Can you please clarify this phrase? This differs from MVP where actions route through the View to the Presenter. In MVC, every action in the View correlates with a call to a Controller along with an action. To me, it sounds like the same thing, but I'm sure you're describing something different. – Panzercrisis Oct 19 '16 at 13:24

5

@Panzercrisis I'm not sure if this is what the author meant, but this is what I think they were trying to say. Like this answer - stackoverflow.com/a/2068/74556 mentions, in MVC, controller methods are based on behaviors -- in other words, you can map multiple views (but same behavior) to a single controller. In MVP, the presenter is coupled closer to the view, and usually results in a mapping that is closer to one-to-one, i.e. a view action maps to its corresponding presenter's method. You typically wouldn't map another view's actions to another presenter's (from another view) method. – Dustin Kendall Oct 28 '16 at 17:50

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[up vote]( "This answer is useful")332[down vote]( "This answer is not useful")

I blogged about this a while back, quoting on Todd Snyder's excellent post on the difference between the two:

Here are the key differences between the patterns:

MVP Pattern

View is more loosely coupled to the model. The presenter is responsible for binding the model to the view.

Easier to unit test because interaction with the view is through an interface

Usually view to presenter map one to one. Complex views may have multi presenters.

MVC Pattern

Controller are based on behaviors and can be shared across views

Can be responsible for determining which view to display

It is the best explanation on the web I could find.

](http://stackoverflow.com/users/63550/peter-mortensen)

edited May 4 '15 at 3:28

[

Peter Mortensen

10.9k1575109

answered Aug 5 '08 at 10:21

[

](http://stackoverflow.com/users/372/jon-limjap)

Jon Limjap

66.5k1485141

6

I don't understand how in the view can be coupled more or less closely to the model when in both cases the entire point is to completely decouple them. I'm not implying you said something wrong--just confused as to what you mean. – Bill K Oct 5 '11 at 0:25

I am confused by this answer (as with the accepted one) as then MVC (after "View" chosen) = MVP? In that case, how is it different than a MVP showing a different Tabbed Page (e.g. hide other Tabs); the "View" is now different? (Granted each Tab could have it's own MVP, but then why couldn't each Panel? Each Button?) – user166390 Jun 15 '12 at 19:36

8

@pst: with MVP it's really 1 View = 1 Presenter. With MVC, the Controller can govern multiple views. That's it, really. With the "tabs" model imagine each tab having its own Presenter as opposed to having one Controller for all tabs. – Jon Limjap Jun 29 '12 at 9:46

3

Originally there are two types of controllers: the one which you said to be shared across multiple views, and those who are views specific, mainly purposed for adapting the interface of the shared controller. – none Nov 11 '13 at 14:12

@JonLimjap What does it mean by one view anyway? In the context of iOS programming, is it one-screenful? Does this make iOS's controller more like MVP than MVC? (On the other hand you can also have multiple iOS controllers per screen) – huggie Mar 19 '14 at 7:55

show 2 more comments

[up vote]( "This answer is useful")270[down vote]( "This answer is not useful")

This is an oversimplification of the many variants of these design patterns, but this is how I like to think about the differences between the two.

MVC

MVP

](http://stackoverflow.com/users/157605/phyxx)

answered Jul 6 '13 at 22:18

[

Phyxx

8,00253967

5

This is a great depiction of the schematic, showing the abstraction and complete isolation of any GUI related (view stuff) from the API of the presenter. One minor point: A master presenter could be used where there is only one presenter, rather than one per view, but your diagram is the cleanest. IMO, the biggest difference between MVC/MVP is that MVP tries to keep the view totally void of anything other than display of the current 'view state' (view data), while also disallowing the view any knowledge of Model objects. Thus the interfaces, needing to be there, to inject that state. – Clay Ferguson Oct 15 '13 at 3:30

Awesome reply, mainly for your picture which shows exactly the existence of a single controller in MVC. – none Nov 11 '13 at 14:08

2

Good picture. I use MVP quite a lot, so I'd like to make one point. In my experience, the Presenters need to talk to one another quite often. Same is true for the Models (or Business objects). Because of these additional "blue lines" of communication that would be in your MVP pic, the Presenter-Model relationships can become quite entangled. Therefore, I tend to keep a one-to-one Presenter-Model relationship vs. a one-to-many. Yes, it requires some additional delegate methods on the Model, but it reduces many headaches if the API of the Model changes or needs refactoring. – splungebob Feb 28 '14 at 14:45

2

The MVC example is wrong; there's a strict 1:1 relationship between views and controllers. By definition, a controller interprets human gesture input to produce events for the model and view alike for a single control. More simply, MVC was intended for use with individual widgets only. One widget, one view, one control. – Samuel A. Falvo II Apr 5 '14 at 15:34

1

@StuperUser -- Not sure what I was thinking when I wrote that. You're right, of course, and looking back on what I wrote, I have to wonder if I had some other context in mind which I failed to articulate. Thanks for the correction. – Samuel A. Falvo II Jan 11 '16 at 23:40

show 3 more comments

[up vote]( "This answer is useful")154[down vote]( "This answer is not useful")

Here are illustrations which represent communication flow

](http://stackoverflow.com/users/202940/ashraf-bashir)

answered Sep 12 '14 at 20:47

[

Ashraf Bashir

5,28363467

14

I have a question regarding the MVC diagram. I don't get the part where the view goes out to fetch data .I would think the controller would forward to the view with the data needed. – Brian Rizo May 12 '15 at 21:07

23

If a user clicks a button, how is that not interacting with the view? I feel like in MVC, the user interacts with the view more than the controller – Jonathan Leaders Aug 12 '15 at 3:28

3

I know this is an old answer - but could anyone respond on @JonathanLeaders point? I'm coming from a winforms background unless you did some very unique coding, when you click the UI/View gets knowledge of that click before anything else. At least, as far as I know? – Rob P. Jan 4 '16 at 14:44

2

@RobP. I think these kinds of charts always tend to be either too complex, or too simple. Imo the flow of the MVP chart also holds true for a MVC application. There might be variations, depending on the languages features (data binding / observer), but in the end the idea is to decouple the view from the data/logic of the application. – Luca Fülbier Jan 17 '16 at 9:37

4

@JonathanLeaders People have really different things in mind when they say "MVC". Person who created this chart had probably classic Web MVC in mind, where the "user input" are HTTP requests, and "view returned to user" is a rendered HTML page. So any interaction between a user and a view are "not existent" from the perspective of an author of classical Web MVC app. – cubuspl42 Jun 12 '16 at 14:38

show 4 more comments

[up vote]( "This answer is useful")133[down vote]( "This answer is not useful")

MVP is not necessarily a scenario where the View is in charge (see Taligent's MVP for example). I find it unfortunate that people are still preaching this as a pattern (View in charge) as opposed to an anti-pattern as it contradicts "It's just a view" (Pragmatic Programmer). "It's just a view" states that the final view shown to the user is a secondary concern of the application. Microsoft's MVP pattern renders re-use of Views much more difficult and conveniently excuses Microsoft's designer from encouraging bad practice.

To be perfectly frank, I think the underlying concerns of MVC hold true for any MVP implementation and the differences are almost entirely semantic. As long as you are following separation of concerns between the view (that displays the data), the controller (that initialises and controls user interaction) and the model (the underlying data and/or services)) then you are acheiving the benefits of MVC. If you are acheiving the benefits then who really cares whether your pattern is MVC, MVP or Supervising Controller? The only real pattern remains as MVC, the rest are just differing flavours of it.

Consider this highly exciting article that comprehensively lists a number of these differing implementations. You may note that they're all basically doing the same thing but slightly differently.

I personally think MVP has only been recently re-introduced as a catchy term to either reduce arguments between semantic bigots who argue whether something is truly MVC or not or to justify Microsofts Rapid Application Development tools. Neither of these reasons in my books justify its existence as a separate design pattern.

edited Feb 22 '13 at 16:35

answered Aug 25 '08 at 21:22

[

](http://stackoverflow.com/users/1143/quibblesome)

Quibblesome

18.4k84789

15

I've read several answers and blogs about the differences between MVC/MVP/MVVM/etc'. In effect, when you are down to business, it's all the same. It doesn't really matter whether you have an interface or not, and whether you are using a setter (or any other language feature). It appears that the difference between these patterns was born from the difference of various frameworks' implementations, rather than a matter of concept. – Michael Mar 7 '11 at 22:36

5

I wouldn't call MVP an anti-pattern, as later in the post "..the rest [including MVP] are just differing flavours of [MVC]..", which would imply that if MVP was an anti-pattern, so was MVC... it's just a flavor for a different framework's approach. (Now, some specific MVP implementations might be more or less desirable than some specific MVC implementations for different tasks...) – user166390 Jun 15 '12 at 19:31

@Quibblsome: “I personally think MVP has only been recently re-introduced as a catchy term to either reduce arguments between semantic bigots who argue whether something is truly MVC or not […] Neither of these reasons in my books justify its existence as a separate design pattern.” . It differs enough to make it distinct. In MVP, the view may be anything fulfilling a predefined interface (the View in MVP is a standalone component). In MVC, the Controller is made for a particular view (if relation's arities may make someone feel that's worth another term). – Hibou57 Feb 20 '13 at 15:50

3

@Hibou57, there is nothing to stop MVC from referencing the view as an interface or creating a generic controller for several different views. – Quibblesome Feb 22 '13 at 16:34

@quibblesome actually, there is. Controllers are, by definition, tightly bound to their corresponding views, for their job is to interpret human gestures (key presses, mouse updates, etc) into events for individual controlson a window. This is why you have a strict one controller, one view relationship. Controllers were neverintended for form-wide use. For form-wide use, Application Model (aka Presentation Model) came into existence, which better suits that purpose. Since non-Smalltalk GUIs don't rely on MVC to implement controls, MVC makes relatively little sense in practice. – Samuel A. Falvo II Apr 5 '14 at 15:31

show 1 more comment

[up vote]( "This answer is useful")71[down vote]( "This answer is not useful")

MVP: the view is in charge.

The view, in most cases, creates its presenter. The presenter will interact with the model and manipulate the view through an interface. The view will sometimes interact with the presenter, usually through some interface. This comes down to implementation; do you want the view to call methods on the presenter or do you want the view to have events the presenter listens to? It boils down to this: The view knows about the presenter. The view delegates to the presenter.

MVC: the controller is in charge.

The controller is created or accessed based on some event/request. The controller then creates the appropriate view and interacts with the model to further configure the view. It boils down to: the controller creates and manages the view; the view is slave to the controller. The view does not know about the controller.

](http://stackoverflow.com/users/63550/peter-mortensen)

edited May 4 '15 at 3:31

[

Peter Mortensen

10.9k1575109

answered Aug 6 '08 at 22:51

[

](http://stackoverflow.com/users/580/brian-leahy)

Brian Leahy

12.8k63859

2

"View does not know about Controller." I think you mean that view has no contact directly with the model? – Lotus Notes Mar 25 '10 at 7:51

view should never know about the model in eiether one. – Brian Leahy Mar 29 '10 at 19:03

2

@Brian: “The View, in most cases, creates it's Presenter.” . I mostly seen the opposite, with the Presenter launching both the Model and the View. Well, the View may launch the Presenter too, but that point is not really the most distinctive. What matters the most happens later during lifetime. – Hibou57 Feb 20 '13 at 15:55

[add a comment]( "Use comments to ask for more information or suggest improvements. Avoid comments like “+1” or “thanks”.")

[up vote]( "This answer is useful")38[down vote]( "This answer is not useful")

MVC (Model View Controller)

The input is directed at the Controller first, not the view. That input might be coming from a user interacting with a page, but it could also be from simply entering a specific url into a browser. In either case, its a Controller that is interfaced with to kick off some functionality. There is a many-to-one relationship between the Controller and the View. That’s because a single controller may select different views to be rendered based on the operation being executed. Note the one way arrow from Controller to View. This is because the View doesn’t have any knowledge of or reference to the controller. The Controller does pass back the Model, so there is knowledge between the View and the expected Model being passed into it, but not the Controller serving it up.

MVP (Model View Presenter)

The input begins with the View, not the Presenter. There is a one-to-one mapping between the View and the associated Presenter. The View holds a reference to the Presenter. The Presenter is also reacting to events being triggered from the View, so its aware of the View its associated with. The Presenter updates the View based on the requested actions it performs on the Model, but the View is not Model aware.

For more Reference

](http://stackoverflow.com/users/5222902/jokerfan)

answered Dec 20 '15 at 2:10

[

JokerFan

3,16241331

But in MVP pattern, when the application loads for the first time , isn't the presenter is responsible to load the first view? Like for example when we load the facebook applicaiton, isn't the presenter responsible to load the login page? – viper Nov 11 '16 at 5:18

[add a comment]( "Use comments to ask for more information or suggest improvements. Avoid comments like “+1” or “thanks”.")

Q:

So... we've had this issue for a while. We're having a huge issue with the push functions, I think.. the issue is whenever it displays in test 2 (and it displays the 'front' of the queue, deque, or whatever) it displays a 0 first and then throughout inputting numbers it throws more 0's in there and throws off what's in the queue overall. Anybody else have this issue? I feel like it's probably a minor issue we're overlooking.

A:

In your default and non-default constructor, you need to be setting your back and front initially to 0. I had a very similar output when I messed with that.

Helpful tip here:

I felt this was more straightforward after getting the Queue done. We ended up keeping the back so that it is always pointing to the next value to be added, which is what we did with the Queue. However, we made it so the front is pointing to the last value added. To do this we are decrementing the front before adding a value but incrementing the back after adding a value. This was the simplest way I could think of. We are using a size variable, so we don't care about keeping an extra value in the array and the calculations are much simpler.

I wonder if anyone was able to get this to work without using a size variable.

reply:

The main change was in the last part we used a deque of pointers because we were having trouble instantiating separate objects without doing it that way.

question:

While testbed checks for the wrap in the deque, it expects four items to be on a deque with a capacity of four. According ot the textbook, one empty slot must be left between the back and the For a single element in the container the back is the front. With a dequeue filled with a single element, whether you use d.back() or d.front() you should get the element that is in there. Does that make sense?

answer:

I recommend modifying your back logic, so that _back is representing the last item in the container, just like _front represents the first item in the container. For instance my back() method returns like this:

return deque[myBack]; // in queue class this was return deque[myBack - 1];

Let me know if this is helpful.

week03 notes

need to make sure prices and batch index match up

and more importantly, that the batch is actually being copied over correctly from tempBatch in the sell() function…

index is size 1 for the newly-modified currentBatch that needs to be inserted into the Batch queue.

https://www.dropbox.com/s/mkzb2zu1dvw5d41/Screenshot%202016-11-18%2003.13.31.png?dl=0

this screenshot shows how ‘temp’ goes from being 3 to suddenly being 0 within 3 lines. Not sure how this is happening. See lines 131 - 134 (roughly) of stock.h. Either the assignment operator ain’t workin, or the copy constructor… i dunno. But i better check both out in the morning.

UPDATE: ok, for newly created Queues, it uses the copy constructor to copy over everything and then it’s done. But for Queues that have already existed, like priceHistory_cents, it does the copy constructor, THEN the assignment operator, THEN the copy constructor again. What the heck?! Why?! And then the data is lost that way. Why? I have no idea.

i don’t understand entirely what went wrong, but wow…It looks like it may have been the assignment operator. I need to understand those things better. I swear...

###First, it's important to recognize that some operators MUST be overloaded in the class declaration (inline, member function) and others outside of it (out-of-line, non-member).

Member: (from CS 165 text)

...it is defined as a member function, either prototyped in the class definition or completely defined as inline in the class definition.
- Also, remember: (from CS 165 text)

...The left-hand-side parameter is hidden. Recall from Chapter 2.1 that a function modifying an object needs to pass the object as a parameter. In the case of member functions, this parameter is hidden and given the name this. The same is true with member operator overloading. .

As I was reading the textbook regarding parameters (4.9.3, pg 174) I found myself reading and re-reading the same few sentences, which said:

When a function is called, the values of the actual parameters specified in the call are, in effect, copied into their corresponding formal parameters, which behave exactly like local variables. Because references are passed as the actual parameters of objects, the called function has access to the objects and can change them, thereby providing the semantics of pass-by-reference parameters.

Looking back, these two sentences probably could have been phrased a lot better, because what it sounds like this is saying is two contradictory statements:

When parameters are passed to a function, it's only a copy of the value instead of a reference.
When parameters are passed to a function, the function can change stuff by reference.

That was a little confusing for me. But I think I figured it out.

What I missed was the fact that it mentioned objects. An object in JS is something like this:

var person = {

firstName:"John",

lastName:"Doe",

age:50,

eyeColor:"blue"

};

The object is person, and the properties are firstName, lastName, age and eyeColor. The values of these properties are (respectively) "John", "Doe", "50" and "blue". When you pass a property value to a function, it is only a copy of the value, not a reference to the value. This part is different from C++ because you can’t use the & operator to pass the value by reference.

However!

If you pass an object to a function, like person, you CAN access the property values by reference, like this:

person.lastName

or

person["lastName"]

**

Cool right?

Ponder 02: Infix

Alright. So I’m doing a new project. It looks roughly similar to Ponder 01: Vector.

They’re both template classes. I wonder, what IS a stack, anyway? Click here: What is a “stack”?

K. I think I have that somewhat figured out. But stacks require a container class to work. Which one should I use? Am I required to use one? Lemme check. Hmm. No requirement. Maybe it will require me to use a few different ones….

Ah, the book is asking this same question. Page 322.

A stack must store a collection of values, so we begin by considering what kind of storage structure(s) to use.

True dat, textbook. How do you choose then? From what I’m reading from the book, I should probably check the assignment some more to see what the driver program is gonna be asking for… The book chose more than one type.

Ahah! The driver program uses several different data types…

bool
double
int
string
char

Alright great. So….. what’s the advantage of using multiple types? Can’t I just use a good ol’ vector?

For the twitter app:

Application Settings

Keep the "Consumer Secret" a secret. This key should never be human-readable in your application.

Consumer Key (API Key)8j6WzIJmVjtJU17TrTqL72SaX

Consumer Secret (API Secret)7pPRDY4bP0VFk56t3MVYxSYaSTZGmcBraHGx64r8R0SEt5swdx

Access LevelRead and write (modify app permissions)

Ownercameronwlewis

Owner ID454456494

Application Actions

Regenerate Consumer Key and Secret Change App Permissions

Your Access Token

This access token can be used to make API requests on your own account's behalf. Do not share your access token secret with anyone.

Access Token454456494-Jgt8JkY6eyc7s7uYBYaArSKb1M4BbKzDfJ1lkNrG

Access Token SecretBzsBV5Ue7y51g7Y9pfkQyG2dRHkWmHEgnqKX03HRkcFrh

Access LevelRead and write

Ownercameronwlewis

Owner ID454456494

I wanna know the difference!

RequestDispatcher.forward() means the complete control for request processing is forwarded to another servlet.

###What the heck is serializing? According to the official Oracle documentation:

To serialize an object means to convert its state to a byte stream so that the byte stream can be reverted back into a copy of the object. A Java object is serializable if its class or any of its superclasses implements either the java.io.Serializable interface or its subinterface, java.io.Externalizable. Deserialization is the process of converting the serialized form of an object back into a copy of the object.

https://docs.oracle.com/javase/tutorial/jndi/objects/serial.html

Basics of Java-JSON Serialization

From https://futurestud.io/tutorials/gson-getting-started-with-java-json-serialization-deserialization

So let's do some serialization! Serialization in the context of Gson means mapping a Java object to its JSON representation. In the next few tutorials our data is going to get more complex, but for now we'll start with a very plain UserSimple object:

public class UserSimple {  
    String name;
    String email;
    int age;
    boolean isDeveloper;
}

The user object has four properties:

The user's name is a String object
The user's email is also a String object
The user's age is an integer, meaning the age is stored in years (for example 26 and not the exact birthday!)
Finally a boolean flag isDeveloper

Our Android or Java application needs to convert a UserSimple object to its JSON representation. Assuming we keep the member names the same, we would expect such a JSON for Norman, the author of this blog post:

{
  "name": "Norman",
  "email": "[email protected]",
  "age": 26,
  "isDeveloper": true
}

So let's see how we can do the conversion with Gson. First of all, we need to create a Java object for Norman:

UserSimple userObject = new UserSimple(  
    "Norman", 
    "[email protected]", 
    26, 
    true
);

In order to do the serialization, we need a Gson object, which handles the conversion. We can simply use the constructor:

Gson gson = new Gson();

Next, we need to call the function toJson() and pass the UserSimple object:

String userJson = gson.toJson(userObject);

The userJson object contains the following value:

{
  "age": 26,
  "email": "[email protected]",
  "isDeveloper": true,
  "name": "Norman"
}

Gson changed the order of the properties (to alphabetically), but the content is identical! Note how Gson respected the types. String values were wrapped in "", while integer values had no wrapping. We didn't have to mess around with JSON objects or copy single members. A single call to Gson was enough to map the entire object. This comes in extremely handy when we're working with complex data structures. But before going too deep, let's test the other direction. Can Gson create a Java object from the above JSON?

Basics of JSON-Java Deserialization

First of all, we need to create a String, which contains the above-mentioned JSON:

String userJson = "{'age':26,'email':'[email protected]','isDeveloper':true,'name':'Norman'}";

We changed the " to ' to avoid tons of \" escaping. Nevertheless, it works either way. The next step is, as you probably have guessed, to create a Gson instance:

Gson gson = new Gson();

Finally, we've to map from a JSON to a Java object with fromJson():

UserSimple userObject = gson.fromJson(userJson, UserSimple.class);

Note how we've to pass the expected Java object as the second parameter. Otherwise Gson doesn't know what it should map the JSON to. It's not a magician!

If we attach a debugger and check the resulting userObject it'll show us that Gson successfully mapped all properties correctly:

Write JSON to file:

from http://www.java2blog.com/2013/11/gson-example-read-and-write-json.html Create a new class named "GSONWritingToFileExample.java" in src->org.arpit.java2blog

view plain print ?

package org.arpit.java2blog;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.arpit.java2blog.pojo.Country;
import com.google.gson.Gson;
/*
* @Author : Arpit Mandliya
*/
public class GSONWritingToFileExample {
public static void main(String[] args) {
Country countryObj=new Country();
countryObj.setName("India");
countryObj.setPopulation(1000000);
List<String> listOfStates=new ArrayList<String>();
listOfStates.add("Madhya Pradesh");
listOfStates.add("Maharastra");
listOfStates.add("Rajasthan");
countryObj.setListOfStates(listOfStates);
Gson gson = new Gson();
// convert java object to JSON format,
// and returned as JSON formatted string
String json = gson.toJson(countryObj);
try {
//write converted json data to a file named "CountryGSON.json"
FileWriter writer = new FileWriter("E:\\CountryGSON.json");
writer.write(json);
writer.close();
} catch (IOException e) {
e.printStackTrace();
}
System.out.println(json);
}
}

Run above program and content of file CountryGSON.json will be as below :

view plain print ?

{"name":"India","population":1000000,"listOfStates":["Madhya Pradesh","Maharastra","Rajasthan"]}

Read more at http://www.java2blog.com/2013/11/gson-example-read-and-write-json.html\#zHh045mvJEVcpAMF.99

∅ means “empty set"

Setting global environment variables in IntelliJ IDEA and other test config goodies

2012-05-09 | | tool ide

When you run a test from IntelliJ idea, you can customize some of the settings by selecting the list of tests and click Edit Configurations. From there you can change things like:

under which module classpath the test is run
the working directory the test should run from
virtual machine parameters
specific environment variables to use

In Hibernate OGM, we use the same test site for all NoSQL solutions. Changing the module classpath is useful in this situation. We also let you refine via an environment variable which hostname runs say MongoDB.

Unfortunately in Mac OS X, graphic applications do not inherit your .bash_profileconfig. I know, stupid, but what can you do against the Empire? Workaround!

You can set environment variables from each test but it gets tedious quickly. Alternatively, you can set an environment variable globally in IntelliJ - what they call parent environment variables. Go to Preferences and search for Path Variables. Set your global environment variables here and you are good to go. Note that you can ask a test not to inherit these global variables if you want to - in the test configuration.

Update: It turns out I was wrong. Paths Variables is not where global environment variables can be set. If you know where, please let me know.

Update 2: To set an environment variable visible by applications in Mac OS X, use

launchctl setenv MYPATH myvar

then restart your IDE (you might need to log out and back in as well).

Thanks @aagahi for the info. This is not great as it's remote from my IDE but at least that works. BTW, launchctl is supposed to set the data in /etc/lanuchd.confor $HOME/.launchd.conf. Not on my system. If anyone knows where the data is put, I'm interested.

Notes to JetBrains:

your environment variable UI is plain counter productive: either give us a text free area or make tabs and co working
an option to inherit the .bash_profile configuration would be awesome :)

Why is getenv() only returning a variable when run from the terminal, not via web server

[up vote]( "This question shows research effort; it is useful and clear")4[down vote]( "This question does not show any research effort; it is unclear or not useful")favorite

I'm trying to use a custom environment variable for environment detection in my PHP application. I've set the variable system-wide in /etc/environment, rebooted, and checked that it is visible through the terminal using printenv.

I've also checked that it is visible when running PHP at the command line:

php -r 'echo getenv("LOCAL\_DEVELOPMENT");' //returns 'true' as expected

But when I try from a web page script, the variable is not found:

var\_dump(getenv("LOCAL\_DEVELOPMENT")); //returns 'boolean false' (not expected)

I'm using Ubuntu 12.04 LTS with PHP 5.4 and Apache 2.2.

Why is the variable not visible from a web script, and how do I fix this?

php

](http://stackoverflow.com/users/942635/mtmacdonald)

asked May 28 '14 at 14:55

[

mtmacdonald

2,48353063

[add a comment]( "Use comments to ask for more information or suggest improvements. Avoid answering questions in comments.")

1 Answer

[up vote]( "This answer is useful")4[down vote]( "This answer is not useful")accepted

Assuming your using apache server, I think its down to Apache being restricted from the System Environment variables.. for security.

You should set env variables on apache like SetEnv LOCAL_DEVELOPMENT true or even better SetEnv APPLICATION_ENV development is generally considered the standard.

](http://stackoverflow.com/users/2032367/raggamuffin-420)

answered May 28 '14 at 15:00

[

RaggaMuffin-420

1,5571513

thanks, makes sense and this works. In my case on Ubuntu, I set this in the appropriate Apache config file in /etc/apache2/sites-available. Like so: stackoverflow.com/questions/10902433 – mtmacdonald May 28 '14 at 15:10

Mac OS X

To set an environment variable on Mac OSX, first open a terminal window. If you are setting the environment variable to run jobs from the command line, use the following command:

export variable=value

where variable is the name of the environment variable (such as SCHRODINGER) and value is the value you want to assign to the variable, (such as /opt/schrodinger/suites2013). You can find out which environment variables have been set with the env command.

If you are setting the environment variable globally to use with applications, use the commands given below. The environment variables set by these commands are inherited by any shell or application.

OS X 10.6, 10.7

To set an environment variable, enter the following command:

defaults write ~/.MacOSX/environment variable "value"

To find out which environment variables have been set, enter the following command:

defaults read ~/.MacOSX/environment

OS X 10.8, 10.9, 10.10

To set an environment variable, enter the following command:

launchctl setenv variable "value"

To find out if an environment variable is set, use the following command:

launchctl getenv variable

To clear an environment variable, use the following command:

launchctl unsetenv variable

Change order of PATH entries on Mac OS X

Posted on February 25, 2011

I wanted to have /usr/local/bin to be listed before /usr/bin in my PATH environment variable.

One way to achieve this would be to add a ~/.profile file with a line like this:

export PATH=/usr/local/bin:$PATH

This would result in /usr/local/bin being listed twice. It wouldn’t hurt but it’s not pretty either.

If you look at /etc/profile, you will see that the initial value of PATH is set by path_helper(8).

The right way to change the order of default paths is to edit /etc/paths. It contains one path per line, in descending order. Mine looks like this:

/usr/local/bin
/usr/bin
/bin
/usr/sbin
/sbin

This entry was posted in Apple, Howto by Daniel Hepper. Bookmark the permalink.

see http://babeljs.io/docs/setup/#installation && https://blog.jetbrains.com/webstorm/2015/05/ecmascript-6-in-webstorm-transpiling#babelfilewatcher
make sure WebStorm is selected, follow instructions
Make sure ECMAScript6 is selected in WebStorm preferences
Setup ESLint, make sure it's active in current project in Preferences. Install path: /usr/local/lib/node_modules/eslint
see https://www.jetbrains.com/help/webstorm/2016.3/using-javascript-code-quality-tools.html#installESLint
and maybe also see https://www.jetbrains.com/help/webstorm/2016.3/eslint.html
possibly also use Google Closure Linter, or gjslint. Install path: /usr/local/bin/gjslint
OR run which gjslint in Terminal to find the path
here's a sample config file to use: https://gist.github.com/manakor/10018231
https://gist.github.com/manakor/10018231#file-gslint-conf
Use Shadow DOM.
Use Flow. ##If background processes keep looping and restarting (especially with Babel), go to 'File'->'Invalidate Cache/Restart', then select 'Invalidate and Restart'.

##Babel and Google Closure linter/gjslint don't seem to play nice together. I think this is what is making Babel loop on in the background.

#EDIT: Nope, babel is just messed up. Gosh dangit that sucks. Ughhhh

#EDIT: FIGURED IT OUT. Babel needs to be installed locally to every project. Go to their website to figure it out.

you can install NPM packages natively from WebStorm! Just search 'NPM' in the Preferences and you'll see it. Just make sure that you put in -g in the options to have it installed globally so that WebStorm can see it in the Packages menu. Otherwise it won't show up.

babel-eslint vs eslint-plugin-babel vs eslint-plugin-react?

[up vote]( "This question shows research effort; it is useful and clear")4[down vote]( "This question does not show any research effort; it is unclear or not useful")favorite

What is the difference between the libraries? babel-eslint [https://github.com/babel/babel-eslint]eslint-plugin-babel [https://github.com/babel/eslint-plugin-babel] eslint-plugin-react [https://github.com/yannickcr/eslint-plugin-react]

reactjs babeljs eslint

](http://stackoverflow.com/users/2134720/ahmed-abbas)

asked Feb 16 at 0:01

[

Ahmed Abbas

633719

[add a comment]( "Use comments to ask for more information or suggest improvements. Avoid answering questions in comments.")

1 Answer

[up vote]( "This answer is useful")4[down vote]( "This answer is not useful")accepted

babel-eslint is a parser that allows you to use ESLint with code that is supported by Babel (ES6+ features, flow types, etc.). ESLint on it's own only supports ES6, JSX and object rest/spread, anything beyond that requires babel-eslint. eslint-plugin-babel is a plugin that fixes/adds a few rules that work with ES7 and beyond features. eslint-plugin-react is a plugin that adds a bunch of rules specific to React applications.

Hey guys,

Not sure this plugin is needed anymore, since you can use as an eslint parser babel-eslint which now integrate much better with eslint. Also there is another eslint plugin that lints js files and fixes no-undef issues with Flowtypes( https://github.com/gajus/eslint-plugin-flowtype ). Please let me know if for some reason you can't use those 2.

#Don’t even bother using another IDE. Just don’t. Seriously.

Alright. So here we are. After probably oooooh 12-15 hours, I think I finally have this figured out. Here are some things I'm going to cover:

My thoughts on IDEs/editors for JS
My thoughts on JavaScript frameworks
npm
WebStorm
Babel & ES6
Facebook's Flow language
How to set it ALL up in WebStorm

##My thoughts on IDEs/editors for JS OK, I've seen a lot of resources, and they all seem to make a LOT of assumptions about how to accomplish all this.

In fact, that's why right out of the gate, WebStorm is the best tool for JS for the forseeable future, because the amount of configuration for other text editors to enable the same usability and feature set are not only out of control in terms of difficulty, but just downright don't work. The extensions in other apps to enable the same supposed functionality I'm looking for have a staggering amount of bugs and silly workarounds that just kill it for me.

Editors I've tried:

Atom: Buggy extensions. No "IntelliSense"-like linting/parsing of code. No debugging support.
VS Code: Seems really, really promising, but just isn't there with support for lots of frameworks and libraries. Babel implementation is zilch. Horrible, horrible setup for debugging, and every extension has literally buttloads of text-based and terminal-based setup for preferences and settings.
Sublime Text: Tempting cuz of how simple it is, but it's losing support and the extensions and plugins it DOES have are even more difficult to set up than VS Code or Atom. Also, it's a little clunky to use. Not open source either.
CodeRunner: Literally just for running code (if that). And it costs $15-$20. No extensions/plugins that I know of.
Coda: $99 with no discounts I've been able to find with a couple hours of searching. No student discount either. And there's probably only like 20 plugins/extensions available. Absolutely no support for Babel or like...anything else new and cool. Seems really nice and "whooshy" to use, but just...yeah.

Don't reinvent the wheel, Cameron. Seriously.

##My thoughts on JavaScript frameworks

There is a lot of battling going on out there about whether frameworks are a waste of time and compromise the very productivity gains they're supposed to bring. At first I held on to this wholeheartedly (read a lot of sources), and I can certainly see where they're coming from. It causes a lot of splintering among the JS community. And brings extra layers of abstraction, and many of these frameworks/libraries die out and become disused, lacking updates from their creators. What then, of all the time you spent learning them?

Anyway, but I've come to the conclusion that some frameworks/libraries really are worth using, especially if they're created by a large company that has thrown it's support behind it, and if it really does bring productivity gains to its users. But it doesn't seem smart to be an early adopter of a lot of these technologies. Many of them die out, and you've just wasted a lot of time.

For now though, the frameworks/libraries that seem really worth using as of now are:

Node.js (for SURE).
React.js
Flow

##Working Guide on How to set up Babel, Flow, ESLint and other stuff in Webstorm

###First, you gotta npm like crazy for a few minutes (or do it all at once!). This is how you do it.

Edit: before anything else, create a .git folder at the project root with Github Desktop.
Navigate to your project folder in Finder.
Right-click on the project folder, go to 'Services-> New Terminal at Folder'. If you don't see that, know that it can be done. Google it, cuz it's really rad.
type npm init. Go through the menu prompts (doesn't really matter much). We need this to happen because it creates a package.json in the project root and because it creates a node-modules folder with all the fun stuff we want to use in our WebStorm projects.
Now you can install all the rest of the stuff you want with one command, like this: -
npm install --save-dev babel-cli babel-preset-latest eslint babel-eslint .....yadda yadda.
Or one at a time, each with npm install --save-dev in the front, followed by the npm package.
(the --save-dev writes each package name and its "dependency" [don't understand that yet] to the package.json file we created, aaannnd that's important for some reason.

The names of the packages you want are: (they're all listed here too: http://babeljs.io/docs/plugins/)

For Babel:
babel-cli installs Babel
babel-preset-latest preset to transpile the latest/most-recent JS abilities to ES5
babel-eslint uses Babel to lint stuff instead of ESlint, which is good cuz Babel knows more
For Flow:
flow-bin
For Babel transpiling of Flow:
babel-plugin-flow-syntax (well this is handy for other stuff actually)
babel-plugin-transform-flow-comments to turn Flow types into comments
- OR use babel-plugin-transform-flow-strip-types to strip Flow stuff altogether.
For ESLint:
- eslint to make sure we don't mess up in Webstorm
- eslint-plugin-flowtype to make sure flow is linted correctly by eslint
Here's all of that in one chunk for you to copy/paste in the future:

npm install --save-dev babel-cli babel-preset-latest babel-eslint flow-bin babel-plugin-syntax-flow babel-plugin-transform-flow-comments eslint eslint-plugin-flowtype

###Next, we're gonna do some more terminal stuff. Order doesn't matter.

In the same terminal, type flow init to initialize Flow via the .flowconfig file it creates. Don't worry, the command worked. If nothing spat out at you, you're good.
Then, type eslint --init. This will initialize ESLint and create it's config file. A little menu will come up. You should probably just choose the first option to decide on everything for yourself.
We DO want JSX, and we DO want semicolons. And we DO want JSON (actually I don't know, but I think it could only help given the issues I've been having. Honestly it probably doesn't matter).

###Ok! Now we gotta make some files. For the record, ##DO NOT create these create these files in TextEdit, or Textastic, or Sublime (tested these), or Atom, or VS Code (haven't tested these). For some reason, these all create characters in the file (like "\n") that cause bugs later when the settings are being parsed by Babel. Just don't do it.

(I just figured out why! It's technically a JSON-type file, so anything that can recognize JSON is probably good, BUT STILL YOU SHOULD USE WEBSTORM.)

###Instead! Open your project now in Webstorm.

Create a new file entitled .babelrc. This is our config file for Babel.
Now put in the preset and plugins you want in the following format:

{
  "presets": ["latest"],
  "plugins": ["syntax-flow", "transform-flow-comments"]
}

(see https://babeljs.io/docs/plugins/#plugin-preset-paths for more details.)

Lastly, open .eslintrc.json in WebStorm and just put this at the very top to have Babel do the parsing through ESLint--otherwise we're gonna get a bunch of dumb Flow-related errors. Paste this over everything else in the file:

{
  "parser": "babel-eslint",
  "plugins": [
    "flowtype"
  ],
  "rules": {
    "flowtype/boolean-style": [
      2,
      "boolean"
    ],
    "flowtype/define-flow-type": 1,
    "flowtype/delimiter-dangle": [
      2,
      "never"
    ],
    "flowtype/generic-spacing": [
      2,
      "never"
    ],
    "flowtype/no-primitive-constructor-types": 2,
    "flowtype/no-weak-types": 2,
    "flowtype/object-type-delimiter": [
      2,
      "comma"
    ],
    "flowtype/require-parameter-type": 2,
    "flowtype/require-return-type": [
      2,
      "always",
      {
        "annotateUndefined": "never"
      }
    ],
    "flowtype/require-valid-file-annotation": 2,
    "flowtype/semi": [
      2,
      "always"
    ],
    "flowtype/space-after-type-colon": [
      2,
      "always"
    ],
    "flowtype/space-before-generic-bracket": [
      2,
      "never"
    ],
    "flowtype/space-before-type-colon": [
      2,
      "never"
    ],
    "flowtype/type-id-match": [
      2,
      "^([A-Z][a-z0-9]+)+Type$"
    ],
    "flowtype/union-intersection-spacing": [
      2,
      "always"
    ],
    "flowtype/use-flow-type": 1,
    "flowtype/valid-syntax": 1
  },
  "settings": {
    "flowtype": {
      "onlyFilesWithFlowAnnotation": false
    }
  }
}

Shareable configurations


Recommended

This plugin exports a recommended configuration that enforces Flow type good practices.

To enable this configuration use the extends property in your .eslintrc config file:

{
  "extends": [
    "plugin:flowtype/recommended"
  ],
  "plugins": [
    "flowtype"
  ]
}
See ESLint documentation for more information about extending configuration files.


Settings


onlyFilesWithFlowAnnotation

When true, only checks files with a @flow annotation in the first comment.

{
  "settings": {
    "flowtype": {
      "onlyFilesWithFlowAnnotation": true
    }
  }
}

###Now open the WebStorm preferences, under 'WebStorm-> Preferences'.

Under Languages & Frameworks, click JavaScript, then choose ‘Flow’ as the language.
Put in the Flow executable in the node_modules folder in our project.
Its in node_modules-> .bin -> flow.
- Also if you can't see .bin in the file finder window, just press Shift-CMD-'.' at the same time (that's the period button btw) and it'll show up. You relaly gotta press it at the same time. Keep trying.
Afterwards you most likely wanna check every checkbox in that window. Makes Flow a lot more handy.
Alright, now under Languages & Frameworks -> JavaScript, click on Code Quality Tools, then ESLint.
For Node Interpreter, you want node_modules/babel-cli/bin/babel-node.js
Npm package, node_modules/npm
ESLint package: node_modules/eslint
And for the config file, it should find it automatically like it says. if you have problems later, explicity specify it in this window.
And we're done!
Then go to Tools --> File Watchers. We're gonna set up Babel.
Click the + button to add.
I just want you to know, that this window is responsible for a lot of problems. If you don't get this right here, it will screw everything up later.
- I have tried so many configurations for this window copied and pasted from the internet, but honestly the only thing that has worked is leaving it as-is, with the only possible change being in Arguments, replacing "es2015" with "latest". THAT IS IT.
- For the program executable under "Program", use this at your project root: node_modules/.bin/babel
- Also, put a check on "Immediate File Synchronization". Not sure what "Track only root files" does yet, or what it means.
And we're done with the settings! Yay!

##A few last things!

If you wanna use Flow, you have to put this at the top of your .js files:

// @flow

If you wanna debug, you need to MAKE SURE YOU DEBUG THE correct .js FILE IN the dist folder! You can make sure this is set up in the 'Run/Debug Configurations' dialog box in WebStorm.
LASTLY, in the 'Run/Debug Configurations' dialog, make sure the settings are using:
Node interpreter: node_modules/babel-cli/bin/babel-node.js
Node parameters: -r node_modules/babel-core/register
Working directory: your project root
JavaScript file: the matching one in your dist folder that was spit out by Babel!
Also, make sure you set up the 'Browser / Live Edit' function the way you want.
Put a check on 'with JavaScript debugger', too, in that window!
All done!

Other notes for the CamBam pasted from online:

Plugin/Preset Ordering

Ordering matters for each visitor in the plugin.

This means if two transforms both visit the “Program” node, the transforms will run in either plugin or preset order.

Plugins run before Presets.
Plugin ordering is first to last.
Preset ordering is reversed (last to first).

"plugins": [
  "transform-decorators-legacy", // will run first
  "transform-class-properties" // will run second
]
**COPY**

Yes this is confusing, see babel/notes #2. I believe the reason why (for backwards compatability) is that most users had listed “es2015” first and “stage-0” second. stage-0 would run before es2015.

"presets": [
  "es2015", // will run third
  "react", // will run second
  "stage-2" // will run first
]
**COPY**

Plugin/Preset Options

Plugins and Presets can both specify options. You can do so in your config by wrapping it in an array and providing a options object. For example:

{
  "plugins": [
    ["transform-async-to-module-method", {
      "module": "bluebird",
      "method": "coroutine"
    }]
  ]
}

// notice the wrapping array around the preset and option

{
  "presets": [
    ["es2015", { "loose": true, "modules": false }]
  ]
}
**COPY**

Plugin Development

Please refer to the excellent babel-handbook to learn how to create your own plugins.

The simple plugin that reverses names (from the homepage):

export default function ({types: t}) {
  return {
    visitor: {
      Identifier(path) {
        let name = path.node.name;
        // reverse the name: JavaScript -\> tpircSavaJ
        path.node.name = name.split('').reverse().join('');
      }
    }
  };
}
**COPY**

Creating a Preset

To make your own preset, you just need to export a config.

// Presets can contain other presets, and plugins with options.
module.exports = {
  presets: [
    require('babel-preset-es2015'),
  ],
  plugins: [
    [require('babel-plugin-transform-es2015-template-literals'), { spec: true }],
    require('babel-plugin-transform-es3-member-expression-literals'),
  ],
};
**COPY**

For more info, check out the babel handbook section on presets or just look at the es2015 preset repo as an example.

OTHER NOTES:

4[down vote]( "This answer is not useful")accepted

babel-eslint is a parser that allows you to use ESLint with code that is supported by Babel (ES6+ features, flow types, etc.). ESLint on it's own only supports ES6, JSX and object rest/spread, anything beyond that requires babel-eslint. eslint-plugin-babel is a plugin that fixes/adds a few rules that work with ES7 and beyond features. eslint-plugin-react is a plugin that adds a bunch of rules specific to React applications.

Hey guys,

Not sure this plugin is needed anymore, since you can use as an eslint parser babel-eslint which now integrate much better with eslint. Also there is another eslint plugin that lints js files and fixes no-undef issues with Flowtypes( https://github.com/gajus/eslint-plugin-flowtype ). Please let me know if for some reason you can't use those 2.

###One to one

One entity (Customer), one attribute (customer's name)

####One to many

Gym membership to many customers (see screenshot below)

###Many to many Entity to entity. Husband and wife, with as many wives and husbands as they want. Needs an intermediary table.

###Categories of keys

Natural key: has real-world meaning, like an email address.
Surrogate key: computer-generated random number (used as an id, for example)

###Primary Keys Key column within a table which ensures that each row is unique. For example, if you have a user table for a website, each user will have a random generated number as an id, to make sure each user is different in the system and to prevent duplicates, even if they have the same username.

###Foreign Keys Reference to a primary key in another table. Foreign key has to match a row with the exact same primary key. (see screenshot below) {Screenshot: table to the left has customers. First column is the customer's name. Second column is the primary key, and third row is the foreign key that matches the primary key of the gym membership status (1 for Bronze, 2 for Silver, 3 for Gold).

Stacks and Queues

An array is a random access data structure, where each element can be accessed directly and in constant time. A typical illustration of random access is a book - each page of the book can be open independently of others. Random access is critical to many algorithms, for example binary search.

A linked list is a sequential access data structure, where each element can be accesed only in particular order. A typical illustration of sequential access is a roll of paper or tape - all prior material must be unrolled in order to get to data you want.

In this note we consider a subcase of sequential data structures, so-called limited access data sturctures.

Stacks

A stack is a container of objects that are inserted and removed according to the last-in first-out (LIFO) principle. In the pushdown stacks only two operations are allowed: push the item into the stack, and pop the item out of the stack. A stack is a limited access data structure - elements can be added and removed from the stack only at the top. push adds an item to the top of the stack, pop removes the item from the top. A helpful analogy is to think of a stack of books; you can remove only the top book, also you can add a new book on the top.

A stack is a recursive data structure. Here is a structural definition of a Stack:

Applications

The simplest application of a stack is to reverse a word. You push a given word to stack - letter by letter - and then pop letters from the stack.
Another application is an "undo" mechanism in text editors; this operation is accomplished by keeping all text changes in a stack. Backtracking. This is a process when you need to access the most recent data element in a series of elements. Think of a labyrinth or maze - how do you find a way from an entrance to an exit?

Once you reach a dead end, you must backtrack. But backtrack to where? to the previous choice point. Therefore, at each choice point you store on a stack all possible choices. Then backtracking simply means popping a next choice from the stack.
Language processing:
- space for parameters and local variables is created internally using a stack.
- compiler's syntax check for matching braces is implemented by using stack.
- support for recursion

Implementation

In the standard library of classes, the data type stack is an adapter class, meaning that a stack is built on top of other data structures. The underlying structure for a stack could be an array, a vector, an ArrayList, a linked list, or any other collection. Regardless of the type of the underlying data structure, a Stack must implement the same functionality. This is achieved by providing a unique interface:

public interface StackInterface<AnyType>
{
   public void push(AnyType e);

   public AnyType pop();

   public AnyType peek();

   public boolean isEmpty();
}

The following picture demonstrates the idea of implementation by composition.

Another implementation requirement (in addition to the above interface) is that all stack operations must run in constant time O(1). Constant time means that there is some constant k such that an operation takes k nanoseconds of computational time regardless of the stack size.

Array-based implementation

In an array-based implementation we maintain the following fields: an array A of a default size (≥ 1), the variable top that refers to the top element in the stack and the capacity that refers to the array size. The variable top changes from -1 to capacity - 1. We say that a stack is empty when top = -1, and the stack is full when top = capacity-1.

In a fixed-size stack abstraction, the capacity stays unchanged, therefore when top reaches capacity, the stack object throws an exception. See ArrayStack.java for a complete implementation of the stack class.

In a dynamic stack abstraction when top reaches capacity, we double up the stack size.

Linked List-based implementation

Linked List-based implementation provides the best (from the efficiency point of view) dynamic stack implementation.

See ListStack.java for a complete implementation of the stack class.

Queues

A queue is a container of objects (a linear collection) that are inserted and removed according to the first-in first-out (FIFO) principle. An excellent example of a queue is a line of students in the food court of the UC. New additions to a line made to the back of the queue, while removal (or serving) happens in the front. In the queue only two operations are allowed enqueue and dequeue. Enqueue means to insert an item into the back of the queue, dequeue means removing the front item. The picture demonstrates the FIFO access.

The difference between stacks and queues is in removing. In a stack we remove the item the most recently added; in a queue, we remove the item the least recently added.

Implementation

In the standard library of classes, the data type queue is an adapter class, meaning that a queue is built on top of other data structures. The underlying structure for a queue could be an array, a Vector, an ArrayList, a LinkedList, or any other collection. Regardless of the type of the underlying data structure, a queue must implement the same functionality. This is achieved by providing a unique interface.

interface QueueInterface‹AnyType>
{
   public boolean isEmpty();

   public AnyType getFront();

   public AnyType dequeue();

   public void enqueue(AnyType e);

   public void clear();
}

Each of the above basic operations must run at constant time O(1). The following picture demonstrates the idea of implementation by composition.

Circular Queue

Given an array A of a default size (≥ 1) with two references back and front, originally set to -1 and 0 respectively. Each time we insert (enqueue) a new item, we increase the back index; when we remove (dequeue) an item - we increase the front index. Here is a picture that illustrates the model after a few steps:

As you see from the picture, the queue logically moves in the array from left to right. After several moves back reaches the end, leaving no space for adding new elements

However, there is a free space before the front index. We shall use that space for enqueueing new items, i.e. the next entry will be stored at index 0, then 1, until front. Such a model is called a wrap around queue or a circular queue

Finally, when back reaches front, the queue is full. There are two choices to handle a full queue:a) throw an exception; b) double the array size.

The circular queue implementation is done by using the modulo operator (denoted %), which is computed by taking the remainder of division (for example, 8%5 is 3). By using the modulo operator, we can view the queue as a circular array, where the "wrapped around" can be simulated as "back % array_size". In addition to the back and front indexes, we maintain another index: cur - for counting the number of elements in a queue. Having this index simplifies a logic of implementation.

See ArrayQueue.java for a complete implementation of a circular queue.

Applications

The simplest two search techniques are known as Depth-First Search(DFS) and Breadth-First Search (BFS). These two searches are described by looking at how the search tree (representing all the possible paths from the start) will be traversed.

Deapth-First Search with a Stack

In depth-first search we go down a path until we get to a dead end; then we backtrack or back up (by popping a stack) to get an alternative path.

Create a stack
Create a new choice point
Push the choice point onto the stack
while (not found and stack is not empty)
- Pop the stack
- Find all possible choices after the last one tried
- Push these choices onto the stack
Return

Breadth-First Search with a Queue

In breadth-first search we explore all the nearest possibilities by finding all possible successors and enqueue them to a queue.

Create a queue
Create a new choice point
Enqueue the choice point onto the queue
while (not found and queue is not empty)
- Dequeue the queue
- Find all possible choices after the last one tried
- Enqueue these choices onto the queue
Return

We will see more on search techniques later in the course.

Arithmetic Expression Evaluation

An important application of stacks is in parsing. For example, a compiler must parse arithmetic expressions written using infix notation:

1 + ((2 + 3) * 4 + 5)*6

We break the problem of parsing infix expressions into two stages. First, we convert from infix to a different representation called postfix. Then we parse the postfix expression, which is a somewhat easier problem than directly parsing infix.

Converting from Infix to Postfix. Typically, we deal with expressions in infix notation

2 + 5

where the operators (e.g. +, *) are written between the operands (e.q, 2 and 5). Writing the operators after the operands gives a postfix expression 2 and 5 are called operands, and the '+' is operator. The above arithmetic expression is called infix, since the operator is in between operands. The expression

2 5 +

Writing the operators before the operands gives a prefix expression

+2 5

Suppose you want to compute the cost of your shopping trip. To do so, you add a list of numbers and multiply them by the local sales tax (7.25%):

70 + 150 * 1.0725

Depending on the calculator, the answer would be either 235.95 or 230.875. To avoid this confusion we shall use a postfix notation

70  150 + 1.0725 *

Postfix has the nice property that parentheses are unnecessary.

Now, we describe how to convert from infix to postfix.

Read in the tokens one at a time
If a token is an integer, write it into the output
If a token is an operator, push it to the stack, if the stack is empty. If the stack is not empty, you pop entries with higher or equal priority and only then you push that token to the stack.
If a token is a left parentheses '(', push it to the stack
If a token is a right parentheses ')', you pop entries until you meet '('.
When you finish reading the string, you pop up all tokens which are left there.
Arithmetic precedence is in increasing order: '+', '-', '*', '/';

Example. Suppose we have an infix expression:2+(4+3*2+1)/3. We read the string by characters.

'2' - send to the output.
'+' - push on the stack.
'(' - push on the stack.
'4' - send to the output.
'+' - push on the stack.
'3' - send to the output.
'*' - push on the stack.
'2' - send to the output.

Evaluating a Postfix Expression. We describe how to parse and evaluate a postfix expression.

We read the tokens in one at a time.
If it is an integer, push it on the stack
If it is a binary operator, pop the top two elements from the stack, apply the operator, and push the result back on the stack.

Consider the following postfix expression

5 9 3 + 4 2 * * 7 + *

Here is a chain of operations

Stack Operations              Output
--------------------------------------
push(5);                        5
push(9);                        5 9
push(3);                        5 9 3
push(pop() + pop())             5 12
push(4);                        5 12 4
push(2);                        5 12 4 2
push(pop() * pop())             5 12 8
push(pop() * pop())             5 96
push(7)                         5 96 7
push(pop() + pop())             5 103
push(pop() * pop())             515

Note, that division is not a commutative operation, so 2/3 is not the same as 3/2.

Victor S.Adamchik, CMU, 2009

###Tag vs element vs attribute vs property tags are <these> <things>. elements are what go in between <these> I'm an element <things> attributes are the stuff that goes inside <these like="this"> (see 'like'? That's an attribute). properties are the stuff in quotes.

HTML tags vs. elements vs. attributes

When talking (or writing) about HTML, it is common for many people to refer to just about everything as "tags" instead of using the proper terms: "tag", "element", and "attribute". A lot of the time what the author really means can be figured out by looking at the context, but sometimes it can be confusing.

Using the correct terminology is not very difficult. It will also make it easier for others to correctly interpret what you mean, not to mention lend more credibility to what you have to say. This is pretty basic knowledge, but in case you need to refresh your memory I've written a quick explanation of tags, elements, and attributes in HTML.

HTML elements

An element in HTML represents some kind of structure or semantics and generally consists of a start tag, content, and an end tag. The following is a paragraph element:

<p>
This is the content of the paragraph element.
</p>

HTML tags

Tags are used to mark up the start and end of an HTML element.

A start tag consists of an opening angle bracket (<) followed by the element name, zero or more space separated attribute/value pairs, and a closing angle bracket (>).

A start tag with no attributes:

<p>

A start tag with an attribute:

<p class="info">

End tags consist of an opening angle bracket followed by a forward slash, the element name, and a closing angle bracket:

</p>

There are also some elements that are empty, meaning that they only consist of a single tag and do not have any content. In HTML, such tags look just like opening tags:

<br>

The syntax is slightly different in XHTML. Empty elements must either have an end tag or the start tag must end with />. In order to ensure backward compatibility with HTML the most common way of writing empty elements in XHTML is to use minimised tag syntax with a space before the trailing />:

<br />

HTML attributes

An attribute defines a property for an element, consists of an attribute/value pair, and appears within the element's start tag. An element's start tag may contain any number of space separated attribute/value pairs.

The most popular misuse of the term "tag" is referring to alt attributes as "alt tags". There is no such thing in HTML. Alt is an attribute, not a tag.

<img src="foobar.gif" alt="A foo can be balanced on a bar by placing its fubar on the bar's foobar.">

Document sections

Another related term is "section". An HTML document is divided into a "head" section (the contents of the head element) and a "body" section (the contents of the body element).

Not nitpicking

You may call this nitpicking, but I don't think it is. Sure, most of the time people will understand what you mean even if you call everything a "tag". But by using the correct terminology you reduce the risk of being misunderstood, and you will sound more professional, so you really have nothing to lose by learning the difference.

#Ok, lemme get this straight: Questions for Team Activity 6:

MainActivity needs to implement ListActivity. Why again? 1a) What is ListActivity, anyway? Activities?
So...ArrayAdapter is an adapter class, to, well...adapt data types, it seems. Right?

###What are activities? From Google's documentation:

There are four different types of app components:

Activities.

Services.

Content providers.

Broadcast receivers.

An activity is the entry point for interacting with the user. It represents a single screen with a user interface.

Here's an important point:

You implement an activity as a subclass of the Activity class.

An activity is just an empty screen. Activity is also the name of a class. So, to make an Android app, you must have a 'main' portion of the app, called MainActivity. It is considered a subclass of Activity. Since MainActivity is the starting point for your app, you need to at least implement onCreate() from Activity. This will be the entry point/constructor for your app.

###Okay, got it. Now why do I need to implement ListActivity? (see ListActivity doc )

First, it's important to understand that ListActivity is also an Activity! It's just a certain type of an activity. ListActivity is an activity (or screen) that is able to display items in a list.

To do this, it binds to a data source that can be displayed in a list, like an array. And to accomplish that, "ListActivity hosts a ListView object that can be bound to different data sources"(link), such as an array.

So if you want or need to use ListView like the assignment instructions tell you to, ListActivity is the way to go, since you're making an activity that uses a list of items .

ListActivity...is an activity that includes a ListView as its only layout element by default

Boom, roasted!

###Alright. What about ListView? What the heck is that and how do I use it? (see ListView doc )

Good question. According to Google, a ListView is

...a view group that displays a list of scrollable items. The list items are automatically inserted to the list using an Adapter that pulls content from a source such as an array or database query and converts each item result into a view that's placed into the list.

Alright, so we wanna show a list of items. So that means we gotta use ListView, and to use ListView we gotta use an adapter.

###Wow. Okay... Adapter. Why? Go.

(documentation)

Not sure about the 'why' right now. But as the documentation says,

An Adapter object acts as a bridge... to the underlying data for that view...The Adapter provides access to the data items. The Adapter is also responsible for making a View for each item in the data set.

So basically an Adapter makes a View for items in an array.

The Adapter behaves as a middleman between the data source and the AdapterView layout—the Adapter retrieves the data (from a source such as an array or a database query) and converts each entry into a view that can be added into the AdapterView layout.

###OMG. What is a view? (documentation)

A view...

represents the basic building block for user interface components. A View occupies a rectangular area on the screen and is responsible for drawing and event handling... The ViewGroup subclass is the base class for layouts, which are invisible containers that hold other Views...and define their layout properties.

So in the ViewGroup, there's things like <ListView> and <TestView> for displaying (you guessed it), lists and text. You put these view-related tags in main_activity.xml to define the layout.

TL;DR - You need views to display stuff.

###So to display stuff in a list, I need to have a MainActivity that extends ListActivity, and use an Adapter that will make a view to display each item in my list.

Yes, but there's lots of different kinds of Adapters. Remember to use an ArrayAdapter if you wanna make Views for items in an array.

###How do I use an ArrayAdapter? (doc1, doc2)

Use this adapter when your data source is an array. By default, ArrayAdapter creates a view for each array item by calling toString() on each item and placing the contents in a TextView. For example, if you have an array of strings you want to display in a ListView, initialize a new ArrayAdapter using a constructor to specify the layout for each string and the string array:

ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
        android.R.layout.simple_list_item_1, myStringArray);

#-> This may also be helpful. (below)

Adding Listview in Activity

[up vote]( "This question shows research effort; it is useful and clear")0[down vote]( "This question does not show any research effort; it is unclear or not useful")favorite

I want to add ListView as component in my Activity which uses LinearLayout. I tried simple approach as well as suggestion mentioned in Embedding a sized ListView in activity - android

But app crashes on Android 2.2 emulator. I can not inherit my class from ListActivity because I want to include some more components.

Any help or suggestions is appreciated.

android listview

](http://stackoverflow.com/users/812389/navaltiger)

asked Jul 1 '11 at 16:41

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navaltiger

324115

1 Answer