Class and package browser for quickly finding a class, its source, methods and fields, and to be able to explore packages. Completion, class homonyms and disassembly may be enabled. [Open Source, LGPL]

Offers to browse constructor, field, method information with free search for methods and option to view javadocs at method with a browser. Configured by XML document. [Open Source, LGPL]

A class browser and project manager for Emacs. [Open Source, GPL]

Tool that calculates a series of source code metrics for Java. Comes with GUI, Ant integration, and command line option. Site includes documentation and download option. [GPL]

A tool generating HTML reports with source code statistics. Site includes screenshot and download option. [GPL]

Javadoc doclet which generates HTML report of differences between two APIs. [Free]

A tool for visualization (view, search, compare) and manipulation (modify, refactor) of Java Class files. Site includes feature overview, FAQ, download, documentation and tutorial. [Open Source, LGPL]