Inner Class in JAVA

(You can learn about Static Nested Class here )

(You can learn about Non-Static Nested Class here )

(You can learn about Local class here)

4.Anonymous Class

Definition: An anonymous class is a type of inner class that does not have a name(an anonymous class is a special type of nested class that doesn’t have a name). It is typically used for one-time use, such as implementing an interface or extending a class, without the need to create a separate named class.

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Declaration: In Java, an anonymous class is defined and instantiated simultaneously, usually when required. The basic syntax for defining an anonymous class is as follows:

new <InterfaceName>() {
    // Anonymous class body
    // This can include method implementations, field declarations, etc.
}

or

new <SuperclassName>(<arguments>) {
    // Anonymous class body
    // This can include method implementations, field declarations, etc.
}

example of an anonymous class that implements an interface:

public class Main {
    public static void main(String[] args) {
        // Create an instance of the interface using an anonymous class
        MyInterface myInterface = new MyInterface() {
            @Override
            public void myMethod() {
                System.out.println("Anonymous class implementing MyInterface");
            }
        };

        // Call the method defined in the interface
        myInterface.myMethod();
    }

    // Define a simple interface
    interface MyInterface {
        void myMethod();
    }
}

Use Case:

GUI Development: When using anonymous classes in GUI development, event handling is a typical use case. For instance, you may establish event listeners for buttons or other components in Java Swing by using anonymous classes.

example:

import javax.swing.JButton;
import javax.swing.JFrame;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class Main {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Button Example");

        // Create a button
        JButton button = new JButton("Click Me");

        // Add an action listener using an anonymous class
        button.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                System.out.println("Button Clicked!");
            }
        });

        // Add the button to the frame
        frame.add(button);

        // Set frame size and make it visible
        frame.setSize(300, 200);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
    }
}

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