Hi Pete,
Campbell is right that you really only need the JDK, a text editor, and a command prompt. However, that approach can get tedious, especially when there are so many great IDEs for working with Java, many of which are available for free.
With my book, I've worked hard to make it as easy as possible to use Netbeans or Eclipse. That's why the download for the book includes the projects in the NetBeans and Eclipse formats. Because of that, you can open the projects for each chapter with just a few clicks. The source code is the same for NetBeans and Eclipse, but each
IDE uses different files for configuring the project. If you want to use IntelliJ with this book,
you should be able to import the source code into an IntelliJ project. However, I suspect that's going to require a fair amount of work on your part. I think it would be a lot easier to just install NetBeans (which works similarly to IntelliJ).
I hope this helps. Thanks!