Hi

class A {
int i, j;
}
class B {
int i, j;
}
class C extends A {
int k;
}
class D extends A {
int k;
}
public class ins {
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 object;
object = d; // A reference to d
System.out.println("object now refers to d");
if(object instanceof D)
System.out.println("object is instance of D");
System.out.println();
object = c; // A reference to c
System.out.println("object now refers to c");
if(object instanceof D)
System.out.println("object can be cast to D");
else
System.out.println("object cannot be cast to D");
if(object instanceof A)
System.out.println("object can be cast to A");
System.out.println();

}
}

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http://www.roseindia.net/java/beginners/nonstaticvariable.shtml