DrJava is a Development Environment that can be down load from: 

 [[http://www.drjava.org][drjava.org]]

In order to use DrJava you must first download the Java Development Kit or JDK from: The Oracle Java Download Page

To use DrJava with the bookClasses library classes, you must download and unzip them from the document:

bookClasses-3-9-10.zip

The final set is to add the directory location of the bookClasses on your computer into the Extra Classpath setting of DrJava. This is done by following the Edit menu to the Preference Option.

These directions are discussed in Section 2.2 of the text book. A pdf of this section is available here.