Java Anonymous Classes

What are Anonymous Classes?

• Definition: Anonymous classes are inner classes without a name. They are used to create instances of classes that may not be reused elsewhere in the code.
• Purpose: Primarily, they allow for the creation of a one-time use class that can extend functionality or implement an interface.

Key Concepts

• Use Cases: Commonly used for:
  
  • Implementing interfaces.
  • Extending classes without creating a separate file.

Syntax: An anonymous class is defined at the point of instantiation.

ClassName obj = new ClassName() {
    // method implementations
};

Advantages

• Conciseness: Reduces the need for boilerplate code.
• Encapsulation: Keeps functionality close to its point of use, enhancing readability.

Example

Implementing an Interface

interface Greeting {
    void sayHello();
}

public class Main {
    public static void main(String[] args) {
        Greeting greeting = new Greeting() {
            @Override
            public void sayHello() {
                System.out.println("Hello, World!");
            }
        };
        greeting.sayHello(); // Output: Hello, World!
    }
}

Extending a Class

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

public class Main {
    public static void main(String[] args) {
        Animal dog = new Animal() {
            @Override
            void makeSound() {
                System.out.println("Woof!");
            }
        };
        dog.makeSound(); // Output: Woof!
    }
}

Conclusion

• When to Use: Use anonymous classes for simple implementations of interfaces or classes without overhead.
• Remember: While convenient, overuse can lead to less readable code. Use them judiciously!