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The KeyListener interface is used to track the characters a user types into a text component. The interface is a simple one with only three methods that must be implemented by a class:

public interface KeyListener{

    public void keyPressed(KeyEvent e);
    public void keyReleased(KeyEvent e);
    public void keyTyped(KeyEvent e);


When a class implements the interface it can listen to key events:

inputText.addKeyListener(new KeyListener()
    public void keyPressed(KeyEvent e)
       //when a key is pressed down then this method is called.

    public void keyReleased(KeyEvent e)
       //when the key is released this method is called.
    public void keyTyped(KeyEvent e)
       //In order for this method to be invoked the key combination 
       //must include a proper character. Modifying
       //(e.g., SHIFT, CTRL) or action (e.g., ENTER, DELETE) keys 
       //will not trigger this method by themselves.

To find out more about the KeyListener interface and capturing key events have a look at Using a Key Listener and A KeyListener Example Program.

The KeyEvent object is passed to the KeyListener methods and contains information about the key event that occurs.


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