java

public class A { protected int i; public A (int i) { this.i = i; } }

public class B extends A { public B (int i) { super (i + 1); } public boolean foo (Object myObject) { System.out.println ("foo1"); return ((myObject instanceof B) && (this.i == ((B)myObject).i)); } public boolean foo (B myB, int num) { System.out.println ("foo2"); return (this.i + myB.i) < num; } }

public class C extends B { public C (int i) { super (i); } public boolean foo (int num) { System.out.println ("foo3"); return (this.i != num); } }

public class D extends B { public D (int i) { super (i * 2); } public boolean foo (B myB, int num) { System.out.println ("foo4"); return super.foo (myB, 20); } }

// --- המחלקה Tester (סעיף ב) --- public class Tester { public static void main (String[] args) { A a = new A (1); B b = new B (2); C c = new C (3); D d = new D (4); B bd = new D (5); A ac = new C (6); //*** } }