instanceof

Оператор для проверки приципа IS-A.

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:

dog instanceof Domestic // true - Dog implements Domestic
dog instanceof Animal   // true - Dog extends Animal
dog instanceof Dog      // true - Dog is Dog
dog instanceof Object   // true - Object is the parent type of all objects

However,

animal instanceof Dog // false

null instanceof Dog // false

And,

dog instanceof Cat // does not even compile!