Are you using Swing? If you are then the easiest thing to do would be to extend
from the AbstractTableModel and
overload the methods which you need to overload. Take a look at the
AbstractTableModel JavaDoc or go to the Sun
tutorials (specifically, the Swing table  tutorial at
java.sun.com/.../table.html ).

You should try to include more information in your next question (Java version,
OS, UI environment [Swing, web, AWT],
etc). It will help us to be able to respond to your questions. Also, read:
www.tuxedo.org/~esr/faqs/smart-questions.html .