Doubt about interfaces in "final Runnable closerRunner = new Runnable()"

Question

Till this date i think that interfaces can not be instantiated because they dont define methods.But one line of code found in a sample program(creating splash screen)creates lots of confusions to me.The line is as follows:
final Runnable closerRunner = new Runnable()
An interface is instantiated using "new" operator.How is this possible ?
Any body help me please.
The whole program follows:
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
class SplashWindow3 extends JWindow
public SplashWindow3(String filename,JFrame f, int waitTime)
super(f);
JLabel l = new JLabel(new ImageIcon(filename));
getContentPane().add(l, BorderLayout.CENTER);
pack();
Dimension screenSize =
Toolkit.getDefaultToolkit().getScreenSize();
Dimension labelSize = l.getPreferredSize();
setLocation(screenSize.width/2 - (labelSize.width/2),
screenSize.height/2 - (labelSize.height/2));
addMouseListener(new MouseAdapter()
public void mousePressed(MouseEvent e)
setVisible(false);
dispose();
final int pause = waitTime;
final Runnable closerRunner = new Runnable()
public void run()
setVisible(false);
dispose();
Runnable waitRunner = new Runnable()
public void run()
try
Thread.sleep(pause);
SwingUtilities.invokeAndWait(closerRunner);
catch(Exception e)
e.printStackTrace();
// can catch InvocationTargetException
// can catch InterruptedException
setVisible(true);
Thread splashThread = new Thread(waitRunner, "SplashThread");
splashThread.start();
public static void main(String [] a)
          //this.setSize(1000,1000);
          JFrame f=new JFrame();
          f.setSize(300,300);
          SplashWindow3 s=new SplashWindow3("shan.jpg",f,100000);
}

Answer 1

That is called an anonymous inner class.
See JLS 15.9.
http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.9