Java Polymorphism using BlueJ

Use this code to practice polymorphism and inheritance with different modifiers for a better understanding how it works in Java.

/** This simple application will help you understand polymorphism
* @version 1.0.0
* @author Zoltan Szabo
*/

public class Polymorphism{
    final static int INDEX=2;

/** application entry point to test inheritance of modifiers
* @param args as a String array for command argument input
*/

   public static void main(String[] args)   {
      SuperClass1[] obj = new SuperClass1[3];
      obj[0]=new SuperClass1();
      obj[1]=new SubClass1();
      obj[2]=new SubSubClass1();
     
      //Direct access to field values
      System.out.println("SuperClass1 public field "+obj[INDEX].x);
      //System.out.println("SuperClass1 private field "+obj[INDEX].y);
      System.out.println("SuperClass1 protected field "+obj[INDEX].z);
      System.out.println("SuperClass1 default field "+obj[INDEX].k);
  
      //Static fields from super class
      System.out.println("SuperClass1 public static field "+SuperClass1.XX);
      //System.out.println("SuperClass1 private static field "+SuperClass1.YY);
      System.out.println("SuperClass1 protected static field "+SuperClass1.ZZ);
      System.out.println("SuperClass1 default static field "+SuperClass1.KK);
  
      //Methods from super class
      System.out.println("SuperClass1 public method "+obj[INDEX].func1());
      //System.out.println("SuperClass1 private method "+obj[INDEX].func2());
      System.out.println("SuperClass1 protected method "+obj[INDEX].func3());
      System.out.println("SuperClass1 default method "+obj[INDEX].func4());
     
   }
}


/** Class that is used as the super class with different modifiers to help understand inheritance
* @version 1.0.0.0
* @author Zoltan Szabo
*/

public class SuperClass1{
    public int x=50;
    private int y=60;
    protected int z=70;
    int k=80;
   
    public static int XX=150;
    private static int YY=160;
    protected static int ZZ=170;
    static int KK=180;
   
/** Super class no-arg constuctor*/
   public SuperClass1(){
      System.out.println("This is the superclass constructor.");
   }



/** Public method in the super class 
* @return x public field from super class
*/
   public int func1(){
        return x;   
   }

/** Private method in the super class 
* @return y private field from super class
*/   private int func2(){
        return y; 
   }

/** Protected method in the super class 
* @return z protected field from super class
*/   protected int func3(){
        return z;
   }

/** Public method in the super class 
* @return k default field from super class
*/   int func4(){
        return k; 
   }
}

/**
*Class that is a child of the SuperClass1 inherits public, protected, and default attributes and methods
*@version 1.0.0
*@author Zoltan Szabo
*/

public class SubClass1 extends SuperClass1{

/** SubClass1class no-arg constuctor*/
   public SubClass1(){
      System.out.println("This is the subclass constructor.");
   }
}

//if you want to implement an interface, use this class
/**
*Class that is a child of the SubClass1 inherits public, protected, and default attributes and methods
*@version 1.0.0
*@author Zoltan Szabo
*/ public class SubSubClass1 extends SubClass1{
/** SubSubClass1 class no-arg constuctor*/
   public SubSubClass1(){
      System.out.println("This is the subsubclass constructor.");
   }
}

//*************** You can add a simple interface as well to practice implementations
/**
 * Simple interface using methods to welcome and hank users
 * @author Zoltan Szabo
 * @version 1.0.0
 */
public interface AddDetails
{
/**
* Welcome the user to your application
* @param y has no significance, only used to practice input parameters
*@return an integer value to practice return data
*/
    public int welcomeMessage(int y);
/**
* Thank the user for using your application
* @param y has no significance, only used to practice input parameters
*@return an integer value to practice return data
*/     public int thankYouMessage(int y);
}