Java Adapter class

Relationship Between Java Adapter Class and Listener Interface

Listeners are used when a programmer intends to use the majority of the methods given in the interface. If a class implements a listener interface directly, it must implement all of the interface's functions, resulting in overly long code. The use of a Java adapter class can aid in the resolution of this issue. A Java adapter class comes in helpful when an event requires a few specialized methods.

To use a Java adapter class, the programmer only needs to create a subclass of it and override the interest methods. Java Adapter classes are advantageous for Java listener interfaces with several methods.

Types of Java Adapter Classes

Java adapter classes can be found in java.awt.event, java.awt.dnd, and javax.swing.event packages. The adapter classes are listed below, along with their listener interfaces.

java.awt.event Adapter classes

java.awt.dnd Adapter classes

javax.swing.event Adapter classes

Example of Java Adapter Classes

Java WindowAdapter 

The WindowAdapter class of AWT is implemented in the following example, and one of its methods, windowClosing() is used to close the frame window.

// importing the necessary libraries  
import java.awt.*;    
import java.awt.event.*;    
  
public class AdapterExample {  
// object of Frame    
    Frame f;    
    
// class constructor  
    AdapterExample() {    
// creating a frame with the title  
        f = new Frame ("Window Adapter");    
// adding the WindowListener to the frame  
// overriding the windowClosing() method   
        f.addWindowListener (new WindowAdapter() {    
            public void windowClosing (WindowEvent e) {    
                f.dispose();    
            }    
        });    
         // setting the size, layout and   
        f.setSize (400, 400);    
        f.setLayout (null);    
        f.setVisible (true);    
    }    
  
// main method  
public static void main(String[] args) {    
    new AdapterExample();    
}    
}    

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Java MouseMotionAdapter 

The MouseMotionAdapter class and its various methods are implemented in the following example to listen to mouse motion events in the Frame window.

// importing the necessary libraries  
import java.awt.*;    
import java.awt.event.*;   
 
// class which inherits the MouseMotionAdapter class  
public class MouseMotionAdapterExample extends MouseMotionAdapter {     

// object of Frame class  
    Frame f;    

// class constructor  
    MouseMotionAdapterExample() {    
// creating the frame with the title  
        f = new Frame ("Mouse Motion Adapter");    
// adding MouseMotionListener to the Frame  
        f.addMouseMotionListener (this);    
 // setting the size, layout and visibility of the frame  
        f.setSize (300, 300);    
        f.setLayout (null);    
        f.setVisible (true);    
    }    

// overriding the mouseDragged() method   
public void mouseDragged (MouseEvent e) {    
// creating the Graphics object and fetching them from the Frame object using getGraphics() method  
    Graphics g = f.getGraphics();    
// setting the color of graphics object  
    g.setColor (Color.ORANGE);    
// setting the shape of graphics object  
    g.fillOval (e.getX(), e.getY(), 20, 20);    
}    

public static void main(String[] args) {    
    new MouseMotionAdapterExample();    
}    
}    

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Output:

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Check out this article - Upcasting and Downcasting in Java

Advantages of Java Adapter Class 

The advantages of Java adapter class area as follows:-

• With the help of the Java adapter class, unrelated classes can work together.
• With the help of a Java adapter class, the same class can be used in multiple ways.
• Users can construct apps with the help of a pluggable kit. As a result, class is reused a lot.
• Java adapter class helps to make classes more visible.
• Java adapter classes allow us to put patterns in a class together.
• Java adapter classes allow courses that are not connected to collaborate more easily.
• Java adapter classes give us the flexibility to use classes in a variety of ways.
• Java adapter classes help to make classes more visible.
• Java adapter classes permit similar patterns to be included in the class.
• Java adapter class comes with a pluggable app development kit.
• Java adapter class increases the reusability of the class.
  
  You can also read about the Multiple Inheritance in Java and, Has-A Relationship in Java.

Frequently Asked Questions

Why do we need Java adapter classes?

Java adapter classes are used by default to implement listener interfaces. We will not have to implement all listener interface functions if we inherit the adapter class. As a result, the code is saved.

What is the adapter class in Java?

An adapter class in Java provides default implementations for methods in listener interfaces, simplifying the creation of event handlers.

Differentiate between the Java Adapter class and Java Listener Interface. 

An adapter class does not need to implement all of the methods in an interface. When only a handful of the interface's methods need to be modified, this method is utilized. A listener's interface must have all of the methods defined in it implemented.

What is an adapter and types?

An adapter is a design pattern that allows interfaces of incompatible objects to work together. Types include class, object, and interface adapters.

Conclusion

In this article, we have extensively discussed the Java adapter classes. We began with a brief introduction to Java adapter classes, followed by a detailed explanation and key examples.

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