import javax.swing.JOptionPane;

// This is an example illustrating inheritance and ploymorphism
class SuperClass {
    int x;
    public SuperClass(int x) {
        this.x = x;
    }
    String method1() {
        return "method1 in SuperClass\n";
    } // end method1

    String method2() {
        return "method2 in SuperClass\n";
    } // end method2

} // end SuperClass

class SubClass extends SuperClass {
    int y;   
    public SubClass(int x,int y) {
        super(x);
        this.y = y;
    }
    String method2() {
        return "method2 in SubClass\n";
    } // end method2

    String method3() {
        return super.method2() + "method3 in SubClass\n";
    } // end method3
} // end SubClass

public class SuperClassSubClassExample {

    public static void main(String[] args) {
        String out = "";
        SuperClass a = new SuperClass(37);
        out += a.method1();
        out += a.method2(); // Since a refers to a SuperClass object this will call
        // the SuperClass method2
        // out += a.method3(); will not compile since a is a SuperClass variable and
        // method3() is not a member of SuperClass
        JOptionPane.showMessageDialog(null, out);
        out = "";
        a = new SubClass(37,73); // a superClass varable can be assigned any of it's subclasses
        out += a.method1();
        out += a.method2(); // Since a refers to a SubClass object now this will call
        // the SubClass method2. This illustrates polymorphism
        // out += a.method3(); will not compile since a is a SuperClass variable and
        // method3() is STILL not a member of the SuperClass
        out += ((SubClass) a).method3(); // a SuperClass variable can be cast to any of it's subclasses
        // so the compiler will not complain. Since a refers to a
        // SubClass object here a runtime error will NOT occur
        JOptionPane.showMessageDialog(null, out);
        a = new SuperClass(111);
        //out += ((SubClass)a).method3(); // a SuperClass variable can be cast to any of it's subclasses
        // so the compiler will not complain. Since a refers to a
        // SuperClass object here a RUNTIME ERROR WILL occur
        SubClass b = new SubClass(111,222);
        JOptionPane.showMessageDialog(null, ((SuperClass) b).method2());
    } // end main
} // end Example 3