Question: after I define a kind of file format, it is dificult for hosting providers to
register it for my site? i can ask that after i paid the service? it must be a mime type properly register at ietf.

thanks in advance

Answer: 
Try adding a [KeyListener](http://java.sun.com/javase/6/docs/api/java/awt/Component.html#addKeyListener%28java.awt.event.KeyListener%29) on the JTextField
You can add a DocumentListener to the JTextField's document i.e.

```
textField.getDocument().addDocumentListener(...);

```