An Extremely Simple Text File Reader Written in Java. (As a beginner's Tutorial)

test.txt

I just read from this file. Isn't java just Awesome? Thanks Dammy.

TextFileReader.java

/* import all packages within the io namespace. (Mostly handles input/output operations)
*  import all packages within the util namespace. (Include all Utilities)
*/
import java.io.*; 
import java.util.*;


/* 
* The general format of a class is the [accessModifier] class [className] {}
*
* A class is the basic building block of all object oriented programming architecture.
* It's simply a blueprint, from which new objects can be instantiated (created) from.
*
* A class contains variables, properties and methods
*/
public class TextFileReader 
{
 	/*
	* This is the main method. It serves as the entry point into your 
	* application. It is required for your application to run
	*
	* During Runtime, it is possible for our application to throw an exception,
	* So we have to let our system know, so as to avoid compilation errors.
	*/
    public static void main (String[] args) 
    {
		/*
        * First, we create a string variable called filename and assign it a value of null.  
		 *  
		 * We know an Exception (Error at Runtime) may occur, so we wrap our executing code within
		 * a try catch block so as to decide how we'll handle it if and when it occurs.
		 *
		 * We grab the filename from the arguments passed or the keyboard input and store it in filename variable 
		 *
		 * Next We call a function that is dedicated towards getting information about the file, while
		 * passing it the filename to read from.     
		 *
        */
       
        String filename = null;

		try {

           filename = (args.length != 0) ? args[0] : getFileToReadFromKeyboardInput();
			
			getInformationAboutFile(filename);
			
		} catch (java.io.IOException e) {
			
			System.out.println ("Sorry, \"" + filename + "\" does not exist in the file location specified.");
			System.out.println ("Note: \"" + filename  + "\" should exist relative to the java file location.");
		}
    }

    /*
    * This method is dedicated to grabbing the filename and location of the file to read from.
    * and then returning the filename so we can pass it into the next function
    */
	private static String getFileToReadFromKeyboardInput() throws java.io.IOException
	{
		// set up the buffered reader to read from the keyboard
		BufferedReader br = new BufferedReader (new InputStreamReader (System.in));

		System.out.println ("Enter file name (file path should be relative to java file location):"); 

		String filename = br.readLine(); // Read line when Input from keyboard has been entered 

		return filename; 
	}
	
    /*
    * This method grabs information about the supplied filename.
    * and may throw an IO Exception if the operation is unsuccessful.
    * Information such as Character Length, and how many words etc.
    */
	private static void getInformationAboutFile(String filename) throws java.io.IOException
	{
		String firstLine;
		String word;

		// set up the buffered reader to read from a file
		BufferedReader br = new BufferedReader (new FileReader (filename));

		firstLine = br.readLine(); // Read the entire line

		System.out.println ("\n\nThe first line of \"" + filename + "\" contains \"" + firstLine + "\"");
		System.out.println ("The first line has " + firstLine.length() + " characters.\n");

		System.out.println ("Breaking the lines into words we get:");
        
        // We use a StringTokenizer Class to break the sentence into individual words
		int numTokens = 0;
		StringTokenizer st = new StringTokenizer (firstLine);

		while (st.hasMoreTokens())
		{
		    word = st.nextToken();
		    numTokens++;
		    System.out.println ("    Word " + numTokens + " is: " + word);
		}
	}
}

usage.md

Compile Java Class

 javac TextFileReader.java

Usage

Option 1: Arguement Based Usage

 java TextFileReader test.txt

Option 2: Command line Input Based Usage

 java TextFileReader

Then follow the prompt