Java Anonymous Class

A Java Anonymous Class is a class without a name that is used to create an instance on the spot, typically for one-time use.

Anonymous classes are commonly used when:

✔ You want to override methods temporarily
✔ You don’t want to create a separate named class
✔ You are implementing an interface or abstract class for short use

Syntax

🧩 Example: Anonymous Class from Abstract Class

abstract class Animal {
abstract void sound();
}public class Main {
public static void main(String[] args) {
Animal dog = new Animal() {
void sound() {
System.out.println("Dog barks using anonymous class");
}
};dog.sound();
}
}

abstract class Animal {

abstract void sound();

}public class Main {

public static void main(String[] args) {

Animal dog = new Animal() {

void sound() {

System.out.println("Dog barks using anonymous class");

}

};dog.sound();

}

✔ Output

Example: Anonymous Class Implementing Interface

interface Greeting {
void sayHello();
}public class Main {
public static void main(String[] args) {
Greeting g = new Greeting() {
public void sayHello() {
System.out.println("Hello from Anonymous Class!");
}
};g.sayHello();
}
}

interface Greeting {

void sayHello();

}public class Main {

public static void main(String[] args) {

Greeting g = new Greeting() {

public void sayHello() {

System.out.println("Hello from Anonymous Class!");

}

};g.sayHello();

}

✔ Output

Anonymous Class Extending a Normal Class

class Car {
void start() {
System.out.println("Car starting...");
}
}public class Main {
public static void main(String[] args) {
Car myCar = new Car() {
void start() {
System.out.println("Anonymous Car Started with Custom Behavior!");
}
};myCar.start();
}
}

class Car {

void start() {

System.out.println("Car starting...");

}

}public class Main {

public static void main(String[] args) {

Car myCar = new Car() {

void start() {

System.out.println("Anonymous Car Started with Custom Behavior!");

}

};myCar.start();

}

✔ Output

Anonymous Class Inside a Method (Practical Example)

✔ Output

🏁 Why Use Anonymous Classes?

Advantage	Description
Saves code	No need to create separate class file
Simple	Great for short-term use
Good for event handling	Common in GUI programming (Swing, Android)

⚠️ Limitations

Limitation	Details
Cannot be reused	Because it has no name
Hard to debug	No class name for trace
Cannot define constructor	Must use class/parent constructor

🎉 Summary

Anonymous classes are temporary, inline subclasses or implementations.
Used when an object needs special behavior only once.
Common in multithreading, event listeners, and callbacks.

Java Anonymous Class