How to use an anonymous inner class in java

Anonymous inner class is an inner class without a name. These Anonymous inner classes are defined and instantiated at the same time. This class is defined in the expression and it starts with a new keyword.

If you want to know about inner classes, Please have a glance at Why Inner Calsses

What are the special features in the inner class :

• Technically you cannot create an object for interface and an abstract class. But using the Anonymous inner class, you can create a single instance to interface and abstract class and within the body, you can implement the unimplemented methods of interfaces and an abstract class.
• The above feature is mainly used in threads and AWT listeners. Example Program:

package explore.innerclass;
package explore.innerclass;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JTextArea;
public class AnonymousClassDemo {
public void createApp() {
JFrame frame =new JFrame();
frame.setTitle("App");
frame.setSize(500, 500);
JButton button =new JButton("click");
button.setToolTipText("button");
button.setBounds(150,95,95,40);
JTextArea text =new JTextArea();
frame.add(button);
frame.add(text);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
//addMouseListener adds the listener.
//MouseAdapter is a abstract class and its not possible to create  object.
//So with anonymous class you can create instance for the abstract class.
 button.addMouseListener(new MouseAdapter() {
 @Override
 public void mouseClicked(MouseEvent e) {
 text.setText("You learnt anonymous class");
}
 });
}
 public static void main(String[] args) {
 AnonymousClassDemo c =new AnonymousClassDemo();
               c.createApp();
}
 }

• In the above code, you create the instance of JFrame and adding the button instance into the Frame. Also, you are creating a text field and that also added with the frame.
• In the addMouseListener class, you are creating an anonymous class. Within the body of the anonymous class , you can implement the abstract method.

Points to be Remembered :

• Anonymous class can access the members of the outer class.
• For an anonymous class, only a single instance can be created.
• Anonymous class can access the local ‘final’ members or effective final members.