Use Of Adapter class in Java

An adapter class in Java enables listener interfaces to be implemented by default. The Delegation Event Model is where the idea of listener interfaces first appeared. It is one of the various methods used by Graphical User Interface (GUI) programming languages like Java to handle events.

The user interacts with the system via connected images and graphics in event-driven GUI programming. This means that any user-initiated action, such as moving the mouse to alter the coordinates of the mouse pointer on the screen, clicking a button, or scrolling a webpage, is regarded as a separate event.

Listener interfaces are implemented by default using Java adapter classes. You won't be required to implement every method of listener interfaces if you inherit from the adapter class. Code is thus saved.

The java.awt.event, java.awt.dnd, and javax.swing.event packages contain the adapter classes.

Benefits of utilising adapter classes 

1. Include helping unrelated classes function together.
2. It offers diverse approaches to using classes.
3. It makes lessons more transparent.
4. It offers a means of incorporating similar patterns into the class.
5. It offers a pluggable development kit for applications.
6. It makes the class more versatile.

Adapter Class	Listener Interface
Mouse Adapter	Mouse Listener
Window Adapter	Window Listener
KeyAdapter	KeyListener
Mouse Motion Adapter	MouseMotion Listener
Container Adapter	Container Listener
Componenet Adapter	Component Listener

MouseAdapter1.java

import java . awt . * ;  
import java . awt . event . * ;  
public class MouseAdapter1 extends MouseAdapter{  
    Frame f1 ;   // Creating a frame
    // Default constructor
    MouseAdapter1 ( ) {  
        f1=new Frame( " M ouse Adapter " ) ;  // Setting the name of the frame as MouseAdapter
        f1 . addMouseListener ( this ) ; 
        f1 . setSize ( 400 , 400 ) ;  // Setting the size of frame 
        f1 . setLayout ( null ) ;  
        f1 . setVisible ( true ) ;  // Giving visibility to the frame
     // This inner class is used to close the window
        f1 . addWindowListener (new WindowAdapter ( ) 
{    
            public void windowClosing (WindowEvent e1) {    
                f1 . dispose ( ) ;    
            }    
        });   
    }  
    public void mouseClicked(MouseEvent e) {  
        Graphics g1=f1 . getGraphics ( ) ;  
        g1 . setColor ( Color . BLACK ) ;  
        g1 . fillOval (e.getX(), e.getY(), 20, 15);    
    }   
public static void main(String[] args) {  
    new MouseAdapter1();  
}  
}

Output

Java Window Adapter Program

This program is used to create windows using awt packages

Adapter.java

// Necessary  packages are imported
import java.awt.*;    
import java.awt.event.*;    
public class Adapter {  
// Creating a Frame  f1  
    Frame f1;    
// default class constructor  
    Adapter() {    
// creating a frame with the title  
        f1 = new Frame ("Adapter Windows");    
// overriding the window closing() method   
        f1.addWindowListener (new WindowAdapter() {    
            public void windowClosing (WindowEvent e1) {    
                f1.dispose();    
            }    
        });    
         // setting the size of the frame
        f1.setSize (350, 450);    
        // setting the size of the frame
        f1 . setLayout ( null ) ;    
        f1 . setVisible ( true ) ;    
    }    
// main method  
public static void main ( String [ ] args ) {    
    new Adapter ( ) ;    
// Default constructor 
// Name of the constructor should be same as class name
}    // main method for the program
}  // Adapter

Output

Java KeyAdapter Program

KeyAdapter1.java

//Importing the required packages
import java.awt.*;    
import java.awt.event.*;    
public class KeyAdapter1 extends KeyAdapter {    
// Creating label and textarea  component variables
    Label l1;    
    TextArea area1;    
    Frame f1;    
// class constructor  
    KeyAdapter1() {    
// creating the Frame with the title  
        f1 = new Frame ("Adapter for Key ");    
// creating the Label  
        l1 = new Label();    
// setting the location of the label   
        l1.setBounds (20, 50, 200, 20);    
// creating the text area  
        area1 = new TextArea();  
        area1.setBounds (20, 80, 300, 300);    
        area1.addKeyListener(this);    
// Adding the label and text area to the frame by using the add  method
        f1.add(l1);  
       f1.add(area1);    
// setting the size  
        f1.setSize (400, 400);  
//layout of the frame  
        f1.setLayout (null);
//visibility of the frame    
        f1.setVisible (true);
        f1.addWindowListener (new WindowAdapter() {    
            public void windowClosing (WindowEvent e) {    
                f1.dispose();    
            }    
        });    
    }    
    public void keyReleased (KeyEvent e) {    
        String text1 = area1.getText();    
// splitting the given String
        String words1[] = text1.split ("\\s");    
        l1.setText ("Words: " + words1.length + " Characters:" + text1.length());    
    }    
  // main method for the program 
    public static void main(String[] args) {    
        new KeyAdapter1();    
    }    
}   

Output