instanceof Operator in Java

Last Updated: 30 September, 2023

In Java, instanceof operator is used to check whether an object is an instance of a specific type (class or subclass or interface) or not. Because it compares the instance to the type, the instanceof operator is also known as the type comparison operator in Java.

It returns a boolean value as an output, true if the object is an instance of the specified type, and false otherwise.

An instanceof operator applied to a variable with a null value returns false.

Syntax:

objectName instanceOf className;

The following example shows how to use the instanceof operator to check if an object is an instance of a particular type:

Example 1: Simple example of Java instanceof operator

public class Example1 { public static void main(String[] args) { // Creating object of Example1 class Example1 object = new Example1(); // Checking object is an instance of Example1 class System.out.println(object instanceof Example1); } }

Output

true

Example 2: Using instanceof operator in Inheritance

// Parent class class Fruit { } // Child class class Apple extends Fruit { } public class Example2 { public static void main(String[] args) { // Creating object of Apple class Apple appleObj = new Apple(); // Checking appleObj is an instance of Apple (child class) if (appleObj instanceof Apple) System.out.println("Yes, appleObj is an instance of Apple."); else System.out.println("No, appleObj is not an instance of Apple."); // Checking appleObj is an instance of Fruit (parent class) if (appleObj instanceof Fruit) System.out.println("Yes, appleObj is an instance of Fruit."); else System.out.println("appleObj is NOT instance of Fruit."); // Note: Checking with Object class as we all know, // Object class is a by default parent class of all Java classes. if (appleObj instanceof Object) System.out.println("appleObj is instance of Object"); else System.out.println("appleObj is NOT instance of Object"); } }

Output

Yes, appleObj is an instance of Apple.
Yes, appleObj is an instance of Fruit.
appleObj is instance of Object

Example 3: instanceof returning false for null

class Test { } public class Example3 { public static void main(String[] args) { Test object = null; // Checking object is an instance of Test class if (object instanceof Test) System.out.println("Yes, object is an instance of Test"); else System.out.println("No, object is not an instance of Test"); } }

Output

No, object is not an instance of Test

Example 4: Parent class object is not an instance of Child class

class Parent { } class Child extends Parent { } public class Example4 { public static void main(String[] args) { // Creating an object of Parent class Parent object = new Parent(); if (object instanceof Child) System.out.println("YES, object is an instance of Child"); else System.out.println("NO, object is not an instance of Child"); } }

Output

NO, object is not an instance of Child

Example 5: Parent reference referring to a Child is an instance of a Child

class Parent { } class Child extends Parent { } public class Example5 { public static void main(String[] args) { // Creating Child class object and assigning reference in the Parent class Parent object = new Child(); if (object instanceof Child) System.out.println("YES, object is an instance of Child"); else System.out.println("NO, object is not an instance of Child"); } }

Output

YES, object is an instance of Child

The instanceof operator can be used in many ways in Java programming, as given below:

• Check if an object is of the expected type before calling a method on it.
• Perform downcasting safely.
• Implement polymorphism.
• Implement type-safety features in Java.