Abstract Class  Example

public abstract class myAbstract {
    myAbstract(){};// this constructor is optional
    public abstract void myMethod( ); //abstract method
    public void myPrint( )    //defined method
    { 
	System.out.println("hello , I am abstract class");
    }
}


public class myExtends extends myAbstract {
    myExtends(){};  //constructor needed 
    public void myMethod( )
    {
	System.out.println("extention of myAbstract myMethod");
    }
}


public class testAbstract {
    public static void main (String args[])
    {
	myExtends a = new myExtends();
	//myAbstract c = new myAbstract();//illegal

	myAbstract c = a;// a reference to the abstract parent can refer to child
	c.myMethod();  // using the parent reference to refer to child
	c.myPrint();
	System.out.println("main ");
	return;
    }

}



 Interface Example



public interface myInterface {
    public abstract void myMethod();
    //    myInterface(int a){}; //illegal line - cannot have constructors in an interface

}


public class implementInterface implements myInterface {
    public void myMethod()
    {  
	System.out.println("hello world");
 
    }
}



public class testInterface {

    public static void main (String args[])
    {
	myInterface a;
	implementInterface b = new implementInterface();
	//a.myMethod();//illegal -  a is a reference not an instance
	a = b;
	a.myMethod();// same as  b.myMethod();
	System.out.println("main ");
	return;
    }

}

© Nachum Danzig December 2003