What does instanceof mean in java

In Java, instanceof is a binary operator used to check whether an object is an instance of a class or an instance of a subclass of a class. Its syntax is "object instanceof class". Among them, object is an object reference, and class is a class name or interface name.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

In Java, instanceof is a binary operator used to check whether an object is an instance of a class or an instance of a subclass of a class.

The syntax is:

object instanceof class

where object is an object reference and class is a class name or interface name.

The function of the instanceof operator is to determine whether object is an instance of class or a derived class of class. If so, returns true; otherwise returns false.

The following is a simple example:

class Animal {
    // ...
}
class Dog extends Animal {
    // ...
}
public class Main {
    public static void main(String[] args) {
        Animal animal = new Dog();
        System.out.println(animal instanceof Animal); // 输出 true
        System.out.println(animal instanceof Dog);    // 输出 true
    }
}

In the above example, animal is an instance of the Dog class and is also an instance of the Animal class, so animal instanceof Animal and animal instanceof Dog both return true.

The instanceof operator is often used for type checking in actual development, especially when dealing with polymorphism.

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