As we all know that: Java do not support multiple inheritance we cannot derive our Applet/Frame/JFrame based classes by any other class at the same time. In that case what can be done is: we can create a new class and that class will be derived from Adapter class. And our newly derived Adapter class can be used as an argument of addXYZListener() method.

Characteristics:

1. Components/Event Sources cannot be easily accessed from Listener methods. We must have object of base class(where we have components) in the Listener class(where we have Listener methods)
2. Event can be applied to a component by passing object of newly created adapter class which extends built in adapter class.
3. View and Controller part can be separated which is a good practice.
4. Not compulsory to define all the methods. No need to write Blank definition if not required.

Code:

import java.awt.*;
import java.applet.*;
import java.awt.event.*;

public class EventDemo5 extends Applet
{
	Button btn;
	static Label lbl;
	public void init()
	{
		btn = new Button("Click Me!");
		lbl = new Label("          ");
		add(btn);
		add(lbl);

		myAdapterClass myObj = new myAdapterClass();
		btn.addMouseListener(myObj);		
	}		 
 }
 
 class myAdapterClass extends MouseAdapter
 {
	public void mouseClicked(MouseEvent e)
	{
	 EventDemo5.lbl.setText("Clicked!");
	} 
  }
  
/*
<applet code="EventDemo5" width="500" height="50"></applet>
*/