Graph eXchange Language
This core package is a set of java classes, packaged in a Java ARchive (jar) file. To use these classes in your project you have to (1) include the jar file in your classpath and (2) use an import statement in the java file of the classes that's using the core package.
  One way of setting the classpath is via the command-line, like this:

javac -classpath ".;gxl.jar" MyClass.java
java -classpath ".;gxl.jar" MyClass

  And put this statement on the top of your java classes:

import net.sourceforge.gxl.*;

For more information on how you use third-party classes, please refer to documentation found on Suns website: www.java.sun.com

The class hierarchy of the core package closely mimics the structure of a GXL document, anyone understanding the basics of GXL should be able to understand how to use these classes. For more information please refer to the API documentation which has been significantly improved to describe more in detail what each class represent and how to use it. A good starting point would be to read the documentation on the GXLDocument and the GXLElement classes.
GXL website