To Demonstrate instanceof operator

Here is a Java Program to Demonstrate instanceof operator

class A {
  int i, j;
}

class B {
  int i, j;
}

class C extends A {
  int k;
}

class D extends A {
  int k;
}

class InstanceOf {
  public static void main(String args[]) {
    A a = new A();
    B b = new B();
    C c = new C();
    D d = new D();

    if(a instanceof A) 
      System.out.println("a is instance of A");
    if(b instanceof B) 
      System.out.println("b is instance of B");
    if(c instanceof C) 
      System.out.println("c is instance of C");
    if(c instanceof A) 
      System.out.println("c can be cast to A");

    if(a instanceof C) 
      System.out.println("a can be cast to C");

    System.out.println();

    // compare types of derived types
    A ob;

    ob = d; // A reference to d
    System.out.println("ob now refers to d");
    if(ob instanceof D) 
      System.out.println("ob is instance of D");

    System.out.println();

    ob = c; // A reference to c
    System.out.println("ob now refers to c");

    if(ob instanceof D) 
      System.out.println("ob can be cast to D");
    else
      System.out.println("ob cannot be cast to D");

    if(ob instanceof A) 
      System.out.println("ob can be cast to A");

    System.out.println();

    // all objects can be cast to Object
    if(a instanceof Object) 
      System.out.println("a may be cast to Object");
    if(b instanceof Object) 
      System.out.println("b may be cast to Object");
    if(c instanceof Object) 
      System.out.println("c may be cast to Object");
    if(d instanceof Object) 
      System.out.println("d may be cast to Object");
  }
}

Output of Above Java Program
a is instance of A
b is instance of B
c is instance of C
c can be cast to A

ob now refers to d
ob is instance of D

ob now refers to c
ob cannot be cast to D
ob can be cast to A

a may be cast to Object
b may be cast to Object
c may be cast to Object
d may be cast to Object