INNER CLASSES

    Java provides the concept of inner classes that is the classes defined within another classes, or even within an expression.

      For understanding the benefits provided by inner classes, consider the applet shown below:

import java.awt.event.*;

import java.applet.*;

import java.awt.*;

public class MyAdapterApplet extends Applet

{

public void init()

{

addMouseListener(new MyAdapter(this));

}

}

class MyAdapter extends MouseAdapter

{

MyAdapterApplet ap;

public MyAdapter(MyAdapterApplet adp)

{

this.ap=adp;

}

public void mouseClicked(MouseEvent e)

{

ap.showStatus("Mouse Clicked");

}

}

In the above example code, there are two top level classes: MyAdapterApplet & MyAdapter. The same code can be improved by using inner classes as shown below:

import java.awt.event.*;

import java.applet.*;

import java.awt.*;

public class MyAdapterApplet extends Applet

{

 public void init()

 {

  addMouseListener(new MyAdapter(this));

 }

 class MyAdapter extends MouseAdapter

 {

  public void mouseClicked(MouseEvent e)

  {

    showStatus("Mouse Clicked");

  }

 }

     Anonymous Inner Class: Anonymous inner class is one that is not assigned a name. The same applet code shown above can be improved by using anonymous inner classes as shown below:

import java.awt.event.*;

import java.applet.*;

import java.awt.*;

public class MyAdapterApplet extends Applet

{

 public void init()

 {

  addMouseListener(new MouseAdapter() {

  public void mouseClicked(MouseEvent e)

  {

    showStatus("Mouse Clicked");

  }

      });

    }

   }