What is difference between Adapter class and listeners in java?

Answer 1

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.

Answer 2

When using a listener you have to implement all the methods that the class provides. An adapter has already implemented empty methods and you can only implement those you need. It is mostly quality of life.