JAVA

Explain about instanceof operator in java

An instanceof in Java is a comparison operator which, given an object instance, 
checks whether that instance is of a specified type (class/sub-class/interface) 
or not. Just like other comparison operators, it returns true or false.

Comparing any object instance with a null type through instanceof operator 
returns a false.
  
Instanceof operator is used to test the object is of which type.

Syntax : <reference expression> instanceof <destination type>
Instanceof returns true if reference expression is subtype of destination type.
Instanceof returns false if reference expression is null.

Java instanceof Keyword

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

Java instanceof

class Main {

  public static void main(String[] args) {

    // create a variable of string type
    String name = "Programiz";
    
    // checks if name is instance of String
    boolean result1 = name instanceof String;
    System.out.println("name is an instance of String: " + result1);

    // create an object of Main
    Main obj = new Main();

    // checks if obj is an instance of Main
    boolean result2 = obj instanceof Main;
    System.out.println("obj is an instance of Main: " + result2);
  }
}

java instanceof example

class Simple1{  
 public static void main(String args[]){  
 Simple1 s=new Simple1();  
 System.out.println(s instanceof Simple1);//true  
 }  
}

Java instanceof Operator

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

    String str = "Programiz";
    boolean result;

    // checks if str is an instance of
    // the String class
    result = str instanceof String;
    System.out.println("Is str an object of String? " + result);
  }
}

Java instanceof

// Java Program to check if an object of the subclass
// is also an instance of the superclass
// superclass
class Animal {
}

// subclass
class Dog extends Animal {
}
class Main {
  public static void main(String[] args) {
    // create an object of the subclass
    Dog d1 = new Dog();
    // checks if d1 is an instance of the subclass
    System.out.println(d1 instanceof Dog);        // prints true
    // checks if d1 is an instance of the superclass
    System.out.println(d1 instanceof Animal);     // prints true
  }
}

instanceof java

@Test
public void givenWhenInstanceIsCorrect_thenReturnTrue() {
    Ring ring = new Ring();
    Assert.assertTrue(ring instanceof Round);
}

Java instanceof Operator

objectName instanceOf className;