instanceof operator is used to check the type of an object at runtime. It is the means by which your program can obtain run-time type information about an object. instanceof operator return boolean value, if an object reference is of specified type then it return true otherwise false. Example

interface Domestic {}
class Animal {}
class Dog extends Animal implements Domestic {}
class Cat extends Animal implements Domestic {}


Imagine a dog object, created with Object dog = new Dog(), then:

System.out.println(dog instanceof Domestic) // true - Dog implements Domestic
System.out.println(dog instanceof Animal)   // true - Dog extends Animal
System.out.println(dog instanceof Dog)      // true - Dog is Dog
System.out.println(dog instanceof Object)   // true - Object is the parent type of all objects

// Object animal = new Animal();,
System.out.println(animal instanceof Dog)   // false

This is because Dog is neither a subtype nor a supertype of Cat, and it also does not implement it.