Java Program on How to use Interface

Program 1

class TestCommand
{
   public static void main(String args[])
  {

                         //  if(args[0].toUpperCase().equals(args[1].toUpperCase()))
                              if(args[0].equalsIgnoreCase(args[1]))
                              System.out.println("Same");
        else                              
                            System.out.println("Not same");
//              System.out.println("Total Arguments: "+ args.length);

//              System.out.println("First Argument: "+ args[0].toUpperCase());
//              System.out.println("First Argument length: "+ args[0].length());
//              System.out.println("Second Argument: "+ args[1].toUpperCase());
//              System.out.println("Second Argument length: "+ args[1].length());
//              System.out.println("Third Argument: "+ args[2].toUpperCase());
 //             System.out.println("Third Argument length: "+ args[2].length());
  }
}

Program 2

 class First implements A
{
   public void myprint()
    {
             System.out.println("This is MyPrint of Class A");
     } 
}

Program 3

 class Second implements A
{
     public void myprint()
    {
             System.out.println("This is MyPrint of Class B");
     } 
}

Program 4

class TestInterface
{
    public static void main(String args[])
    {
               A A1=new Second();
              A1.myprint();

    }

}

Program 5

interface A
{
    void myprint();
    void display();
     int rno=100;
}
class First implements A
{
   public void myprint()
   {
         System.out.println("This is method of class First");    
  }
  public void display(){}
}

class Second implements A
{
   public void myprint()
   {
       System.out.println("This is method of class Second");    
  }
  public void display(){}
}

class Test
{
   public static void main(String args[])
   {
               A A1=new First();
              A1.myprint();
   }
}