JCommon is a free general purpose library for Java that is shared by several other projects, including JFreeChart and JFreeReport.

See: Description

Packages 
Package Description
com.keypoint
A package containing the PNG encoder written by J.
org.jfree
The root package for the JCommon class library.
org.jfree.base  
org.jfree.date
Date classes.
org.jfree.io
Input/output related classes.
org.jfree.layout
Custom layout managers.
org.jfree.resources
General localised resources for the JCommon class library.
org.jfree.text
Utility classes relating to text.
org.jfree.threads
Additional support for multi-threaded programs.
org.jfree.ui
Utility classes for creating user interfaces.
org.jfree.ui.about
Classes for providing information about an application.
org.jfree.ui.about.resources
Resource bundles for items that require localisation.
org.jfree.ui.action  
org.jfree.ui.tabbedui  
org.jfree.util
General utility classes.
org.jfree.xml
XML parser.
org.jfree.xml.attributehandlers  
org.jfree.xml.factory.objects
Object descriptions for the parser.
org.jfree.xml.generator
XML generator.
org.jfree.xml.generator.model
Contains the classes describing the class model used in the JFreeChart XML-parser and writer.
org.jfree.xml.parser
XML parser.
org.jfree.xml.parser.coretypes
XML writers for some core classes.
org.jfree.xml.util
Utility classes for the XML framework.
org.jfree.xml.writer
Core classes for writing XML files.
org.jfree.xml.writer.coretypes
Writers for some core classes.