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instanceof Keyword in Java

Last Updated : 10 Jun, 2026

The instanceof keyword is used to check whether an object belongs to a specific class, subclass, or interface. It compares an object reference with a type and returns a boolean value (true or false). This keyword is commonly used to verify an object's type before performing typecasting, helping to avoid runtime errors such as ClassCastException.

  • It can be used with classes, subclasses, and interfaces.
  • If the reference variable contains null, instanceof always returns false.

Syntax

objectReference instanceof ClassName


Output
true

Explanation: This program creates an object of the GFG class and checks whether it belongs to the same class using the instanceof keyword. Since the object is created from GFG, the condition returns true.

Examples of Java instance of keyword

Here are all the examples of instanceof keywords with their respective cases:

Example: Reating sample classes with a parent-child relationship.


Output
cobj is instance of Child
cobj is instance of Parent
cobj is instance of Object

Explanation: A Child object is created and tested against Child, Parent, and Object classes. Since a child object inherits from its parent and every class inherits from Object, all checks return true.

Example: Instanceof returning false for null 


Output
tobj is NOT instance of Test

Explanation: The reference variable tobj is assigned null and checked using instanceof. Since null does not refer to any object, the expression returns false

Example: Parent object is not an instance of Child  


Output
pobj is NOT instance of Child

Explanation: A Parent object is created and checked whether it is an instance of Child. Since a parent object cannot be treated as a child object, the result is false.

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


Output
cobj is instance of Child

Explanation: A parent reference variable stores a Child object. Although the reference type is Parent, the actual object is Child, so instanceof Child returns true.

Example: Java program to demonstrate that non-method members are accessed according to reference type (Unlike methods which are accessed according to the referred object)


Output
Value accessed through parent reference with typecasting is 10

Application of Java instance of keyword

  • Safe Typecasting: Checks whether an object can be safely cast to another type before performing downcasting.
  • Runtime Type Identification: Determines the actual type of an object during program execution.
  • Inheritance Handling: Verifies relationships between parent and child classes.
  • Polymorphism Support: Helps identify the real object type when a parent reference points to a child object.
  • Avoiding Exceptions: Prevents ClassCastException by validating object types before casting.
  • Object Validation: Ensures that an object belongs to the expected class before accessing specific methods or fields.
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