Interesting libraries

Collections

• Guava contains new useful collection interfaces and classes
• Commons Collections, also in the version for pre 1.5 java.
• GNU Trove — The popular primitive collections framework
• HPPC Collections — Primitive collections framework by Carrot Search

Testing frameworks

• JUnit
• TestNG

Various

• StringTemplate
• AntLR
• Commons Compress
• Jackson Core
• Jackson Databind

Web

• JSoup — HTML library: parsing real world HTML, manipulating and pretty-printing.
• sitemapgen4j — sitemap generation utility
• JSoup Elements — Utilities for generating HTML elements using JSoup conveniently
• JSoup Bootstrap — Utilities for generating Bootstrap pages in JSoup conveniently