What is the 'instanceof' operator used for in Java?

Question

What is the instanceof operator used for? I\'ve seen stuff like

if (source instanceof Button) {
    //...
} else {
    //...
}

Answer 1

The instanceof operator is used to check whether the object is an instance of the specified type. (class or subclass or interface).

The instanceof is also known as type comparison operator because it compares the instance with type. It returns either true or false.

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

If we apply the instanceof operator with any variable that has null value, it returns false.