1. Unit Testing Libraries [JUnit and Mockito]  

2. JSON Parsing libraries [Jackson and Gson]

  3. Logging Libraries [Log4j2 and SLF4j]

4. General-Purpose Libraries [Apache Commons and Guava]

  5. HTTP Libraries [HttpClient]

6. XML Parsing Libraries [Xerces and JAXB]

  7. Excel Reading Libraries [Apache POI]

8. Bytecode Libraries [Javassist and CgLib]

 9. Database Connection Pool Libraries [DBCP and C3P0]  

10. Messaging Libraries [JMS and MQ]  

11. PDF Libraries [iText]

  12. Date and Time Libraries [Joda Time]

13. Collection Libraries [Eclipse Collections]

  14. Email APIs [Java Mail API]

15. HTML Parsing Libraries [Jsoup]

  16. Cryptographic Library

17. Embedded SQL Database Library [H2, HSQL, and Derby]

18. JDBC Troubleshooting Libraries

  19. Networking Libraries [Apache MINA]

20. Lombok [Project Lombok]  

21. Testcontainers  

22. Serialization Libraries [Google Protocol Buffer]