Java Anonymous

Anonymous Class

An anonymous class is a class without a name. It is created and used at the same time.

You often use anonymous classes to override methods of an existing class or interface, without writing a separate class file.

Here, we create an anonymous class that extends another class and overrides its method:

// Normal class
class Animal {
  public void makeSound() {
    System.out.println("Animal sound");
  }
}

public class Main {
  public static void main(String[] args) {
    // Anonymous class that overrides makeSound()
    Animal myAnimal = new Animal() {
      public void makeSound() {
        System.out.println("Woof woof");
      }
    }; // semicolon is required to end the line of code that creates the object

    myAnimal.makeSound();
  }
}

Anonymous Class from an Interface

You can also use an anonymous class to implement an interface on the fly:

// Interface
interface Greeting {
  void sayHello();
}

public class Main {
  public static void main(String[] args) {
    // Anonymous class that implements Greeting
    Greeting greet = new Greeting() {
      public void sayHello() {
        System.out.println("Hello, World!");
      }
    };

    greet.sayHello();
  }
}

Note: When to Use Anonymous Classes? Use anonymous classes when you need to create a short class for one-time use. For example: Overriding a method without creating a new subclass Implementing an interface quickly Passing small pieces of behavior as objects