What is difference between Adapter class and listeners in java?

Java

An Adapter class is just a "blank" implementation of a Listener interface. They're convenience classes made so you don't need to implement all of the methods of an interface.

A good example is the MouseListener interface. Let's say you want to detect when a user clicks on your Component. You only need to implement the mouseClicked method to get that part working. This will leave you with...

public void mousePressed(MouseEvent e) {

}

public void mouseReleased(MouseEvent e) {

}

public void mouseEntered(MouseEvent e) {

}

public void mouseExited(MouseEvent e) {

}

...at the end of your implementation. Ugly. So Java gives us the MouseAdapter class (which gives us the same empty implementations as above). We can use this in place of a MouseListener to try to keep our code cleaner.