gistfile1.java

class X { }
interface A { }
class Y extends X implements A {
    void show() { System.out.println("Hello"); }
}
public class Test {
    public void main(String[] args) {
        X x1 = new X();
        X x2 = new Y();
        ((Y)x2).show();
        ((A)x1).show();
    }
 }