Quiz: OOP

Notes.txt

Access Control:
  private - can only be accessed in the class
  protected - can only be accessed in the class or a subclass
  public - can be accessed anywhere

Modifiers:
  abstract -  a non-access modifier, used for classes and methods
  final - a non-access modifier used for classes, attributes and methods (not changeable)
  finally - executes no matter if the try-except failed or passed
  native - specifies that a method is not implemented in the same java source file
  private - can only be accessed in the class
  protected - can only be accessed in the class or a subclass
  public - can be accessed anywhere
  static - is a non-access modifier used for methods and attributes
  transient - specifies that an attribute is not part of an object's persistent state
  synchronized - specifies that methods can only be accessed by one thread at a time
  volatile - attribute is not cached thread-locally
  strictfp - restrict the precision and rounding of floating-point calculations

Class functions:
  abstract - a non-access modifier, used for classes and methods
  assert - for debugging
  class - used to create a class
  extends - extends a class (indicates that a class is inherited from another class)
  enum - declares an enumerated type
  implements - is used to implement an interface
  import - used to import a package, class or interface
  instanceof - checks whether an object is an instance of a specific class or an interface
  new - creates new objects
  package - creates a package
  return - what a method returns
  interface - used to declare a special type of class that only contains abstract methods
  this - the way you reference the class object
  throws - what error may be thrown
  void - specifies that a method should not have a return value
  super - refers to superclass (parent) objects






OOP stuff

OOP stands for Object-Oriented Programming
OOP gives the code a clear structure

Classes and objects are the two main aspects of OOP
A class is a template for objects, and an object is an instance of a class

Classes consist of attributes and methods

Attributes define what a class is and methods define what a class does

Constructors are methods that are called when the class is initialized
The constructor name must match the class name, and it cannot have a return type
Like normal methods, constructors can have parameters

The Class Object itself is referenced by the special attribute `this`

Static methods & attributes:
  A static method is a class method can be called directly with
  [insert class name here].[insert method name here]() without first creating an object
  A static method must not refer to `this` Therefore, it cannot refer to any class attributes
  A static attribute, similarly, is referenced by [insert class name here].[insert attribute name here] without first creating an object instance

Enums:
  An enum is a special "class" that represents a group of constants

Inner Classes:
  In Java, it is also possible to nest classes

Abstract classes & methods:
  Data abstraction is the process of hiding certain details and showing only essential information to the user.
  Abstraction can be achieved with either abstract classes or interfaces
  
  Abstract class:
   - a restricted class that cannot be used to create objects
  Abstract method:
   - can only be used in an abstract class, and it does not have a body. The body is provided by the subclass 

Interface:
  Another way to achieve abstraction in Java, is with interfaces
  An interface is a completely "abstract class" that is used to group related methods with empty bodies
  To access the interface methods, the interface must be "implemented" by another class with the `implements` keyword



Concepts of Object-Oriented Programming

Inheritance:
  Inheritance is when a class inherits from another class
  In inheritance, you have 2 classes
  You have the subclass (child class)
  and the superclass (parent class)
  To inherit a class, you use the `extends` keyword

Polymorphism:
  Polymorphism occurs when we have many classes used in inheritance
  In the subclass, you can override the method in the superclass

Encapsulation:
  Encapsulation is where you hide certain data from the users
  This is done with private variables
  Since you cannot view private variables outside of the class, you create getter and setter methods to view/modify these variables