What is the advantage of using anonymous classes in modern programming, and why have they not disappeared since their inception?

Anonymous classes in Java allow creating one-time implementations of interfaces or subclasses without the need to explicitly declare a new class with a name. Their advantages:

• Convenience and compactness: enable quick definition of behavior right at the point of use, reducing code size and increasing readability, especially for simple event handlers or callbacks.

• Locality: the code of an anonymous class is located near the point of use, which makes understanding the logic easier.

• Encapsulation: hide implementation details without cluttering the namespace.

Why they haven't disappeared:

• Despite the appearance of lambda expressions (starting from Java 8), which are more concise in many cases, anonymous classes are still necessary when:
  • Creating a class with multiple methods or state.
  • Extending a class (not just implementing an interface).
  • Using more complex logic that lambdas cannot express.

Example of an anonymous class:

button.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
        System.out.println("Button pressed");
    }
});

Thus, anonymous classes remain a useful tool for quickly creating local implementations, complementing the language's capabilities.