Java instanceOf Operator

What is Java instanceOf Operator?

It is a binary operator, that checks whether an object is an instance of a specific class or an interface or subclass. The result will return either true or false.
Also, known as Type Comparison Operator, because it compares the instance with type.

Syntax:

objectName instanceOf className;

Examples 1 :

Java Code

class TUF{  
public static void main(String args[]){  
TUF s=new TUF();  
System.out.println(s instanceof TUF); //true  
}  
}

Output: true

Example 2(String):

Java Code

class Simple{  
  public static void main(String args[]){  
  String str1 = "TUF!";
  if (str1 instanceof String) 
    System.out.println("str1 is an instance of the String"); 
  else
    System.out.println("str1 is NOT an instance of the String"); 
 }  
}

Output: str1 is an instance of the String

Inherited classes:

Java program to check if an object of the subclass is also an instance of the superclass:

Java Code

// superclass
class Animal {
}

// subclass
class Cat extends Animal {
}

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

    // create an object of the subclass
    Cat c1 = new Cat();

    // checks if d1 is an instance of the subclass
    System.out.println(c1 instanceof Cat);        // prints true

    // checks if d1 is an instance of the superclass
    System.out.println(c1 instanceof Animal);     // prints true
  }
}

Output:

true

In the above demo, we have created a subclass of cat that is inherited from superclass Animal. We have created object c1 of cat class.

Another Example:

Java Code

class Bird {}
class Penguin extends Bird {}

class instanceofTest {
  public static void main(String[] args) {
    Penguin pobj = new Penguin();
    Bird bobj = new Bird();

    // Is `child` class instance of `child` class?
    if (pobj instanceof Penguin)
      System.out.println("pobj is instance of Penguin");
    else
      System.out.println("pobj is NOT instance of Penguin");

    // Is `child` class instance of `parent` class?
    if (pobj instanceof Bird)
      System.out.println("pobj is instance of Penguin");
    else
      System.out.println("pobj is NOT instance of Bird");

    // Is the `parent` class instance of `child` class?
    if (bobj instanceof Penguin)
      System.out.println("pobj is instance of Bird");
    else
      System.out.println("pobj is NOT instance of Bird");
  }
}

Output:

pobj is instance of Penguin
pobj is instance of Penguin
pobj is NOT instance of Bird

Java program to demonstrate that instanceof returns false for null:

Java Code

class Test {}

class Main {
  public static void main(String[] args) {
    Test tobj = null;

    // A simple case
    if (tobj instanceof Test)
      System.out.println("tobj is instance of Test");
    else
      System.out.println("tobj is NOT instance of Test");
  }
}

Output: tobj is NOT instance of Test

Application :

It is used when we need to typecast, to check if it’s valid or not using instanceOf Operator.

Special thanks to Amisha Kumari for contributing to this article on takeUforward. If you also wish to share your knowledge with the takeUforward fam, please check out this article