The Structure Package
The “structure package” is a collection of free software for use with the Java Structures text.
Two versions in one
There are two versions of the structure package: the pre-1.5, nonparameterized version, imported as structure.*, and the Java 5-ready version that makes use of parameterized types, imported as structure5.*.  The text begins with the non-generic version, and then switches over after a short discussion of generics.  It is intended that both versions of the software work similarly.
The classes
To make use of the structure package, you must download the JAR file:
Simply place the jar file in your classpath and go.
The source code
Source code for the structure package is found here:
Unzipping this file produces two directories: structure and structure5, containing the respective source files.