instanceof operator example in Java

The instanceof operator compares an object to a specified type. You can use it to test if an object is an instance of a class, an instance of a subclass, or an instance of a class that implements a particular interface. 

The following program:

InstanceofDemo

, defines a parent class (named 

Parent

), a simple interface (named 

MyInterface

), and a child class (named 

Child

) that inherits from the parent and implements the interface. 

class InstanceofDemo {
  public static void main(String[] args) {

    Parent obj1 = new Parent();
    Parent obj2 = new Child();

    System.out.println("obj1 instanceof Parent: " + (obj1 instanceof Parent));
    System.out.println("obj1 instanceof Child: " + (obj1 instanceof Child));
    System.out.println("obj1 instanceof MyInterface: " + (obj1 instanceof MyInterface));
    System.out.println("obj2 instanceof Parent: " + (obj2 instanceof Parent));
    System.out.println("obj2 instanceof Child: " + (obj2 instanceof Child));
    System.out.println("obj2 instanceof MyInterface: " + (obj2 instanceof MyInterface));
  }
}

class Parent{}
class Child extends Parent implements MyInterface{}
interface MyInterface{}







The out put:




obj1 instanceof Parent: true
obj1 instanceof Child: false
obj1 instanceof MyInterface: false
obj2 instanceof Parent: true
obj2 instanceof Child: true
obj2 instanceof MyInterface: true

When using the instanceof operator, keep in mind that null
is not an instance of anything.