You are permitted to use any IDE tool you choose, but you must not submit any code that is not your own work. The final program must have no dependencies on any libraries other than those of the Java 2 Platform.
My recommendation is to avoid IDE's for this project. You will spend far too much time making sure they don't add any code you didn't write. I used jEdit, its a very good editor and it has lots of plugins that help without actually writing code.