Question on "instanceof"

[Yuva Raj Sah]

 
interface I1{
 void method1();
}
 
interface I2{
 void method2();
}
 
class A implements I1 {
public void method1(){ }
}
 
class B extends A implements I2{
public void method2(){}
 
}
 
class AAAA{
 public static void main(String args[]){
 A a = new A();
 B b = new B();
 I1 i = (A) b;
 System.out.println(i instanceof A);
 System.out.println(i instanceof B);
         System.out.println(i instanceof I1);
         System.out.println(i instanceof I2);
}
}
 

Why the code's output is :
ture
true
true
true


:roll: :roll:

[Ernest Friedman-Hill]

The type of the variable "i" doesn't matter at all. All that matters is the type of the object it points to, which is class B. Just remember that "instanceof" is evaluated at runtime.

An instance of B is an instance of A because B extends A.

A B is a B, of course.

A B is an I1 because A implements I1, and B extends A.

And a B is an I2 because B implements I2.

[Ernest Friedman-Hill]

The type of the variable "i" doesn't matter at all. All that matters is the type of the object it points to, which is class B. Just remember that "instanceof" is evaluated at runtime.

An instance of B is an instance of A because B extends A.

A B is a B, of course.

A B is an I1 because A implements I1, and B extends A.

And a B is an I2 because B implements I2.