Java Anonymous Class
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();
}
}
The output will be:
Woof woof
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();
}
}
The output will be:
Hello, World!
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
