Equality, Relational, and Conditional Operators (The Java™ Tutorials > Learning the Java Language > Language Basics)

Equality, Relational, and Conditional Operators (The Java™ Tutorials > Learning the Java Language > Language Basics):

The Type Comparison Operator instanceof

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{}

Output:

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.