How many types of anonymous inner classes are defined in Java?

An anonymous inner class is an inner class which is declared without any class name at all. In other words, a nameless inner class is called an anonymous inner class. Since it does not have a name, it cannot have a constructor because we know that a constructor name is the same as the class name.

We can define an anonymous inner class and create its object using the new operator at the same time in one step.

Syntax

new(argument-list){
   // Anonymous class body
}

Types of Anonymous Inner Class in Java

• Anonymous inner class that extends a class
• Anonymous inner class that implements an interface
• Anonymous inner class as an argument

Anonymous inner class that extends a class

Here a new keyword is used to create an object of the anonymous inner class that has a reference of parent class type.

Example

Live Demo

class Car {
   public void engineType() {
      System.out.println("Turbo Engine");
   }
}
public class AnonymousClassDemo {
   public static void main(String args[]) {
      Car c1 = new Car();
      c1.engineType();
      Car c2 = new Car() {
         @Override
         public void engineType() {
            System.out.println("V2 Engine");
         }
      };
      c2.engineType();
   }
}

Output

Turbo Engine
V2 Engine

Anonymous inner class that implements an interface

Here a new keyword is used to create an object of the anonymous inner class that has a reference of an interface type.

Example

Live Demo

interface Software {
   public void develop();
}
public class AnonymousClassDemo1 {
   public static void main(String args[]) {
      Software s = new Software() {
         @Override
         public void develop() {
            System.out.println("Software Developed in Java");
         }
      };
      s.develop();
      System.out.println(s.getClass().getName());
   }
}

Output

Software Developed in Java
AnonymousClassDemo1$1

Anonymous inner class as an argument

We can use the anonymous inner class as an argument so that it can be passed to methods or constructors.

Example

Live Demo

abstract class Engine {
   public abstract void engineType();
}
class Vehicle {
   public void transport(Engine e) {
      e.engineType();
   }
}
public class AnonymousInnerClassDemo2 {
   public static void main(String args[]) {
      Vehicle v = new Vehicle();
      v.transport(new Engine() {
         @Override
         public void engineType() {
            System.out.println("Turbo Engine");
         }
      });
   }
}

Output

Turbo Engine

Raja

Published on 24-Jun-2019 15:00:49