Top 10 Libraries Every Java Developer Should Know:
1. Java Standard Libraries
2. Mockito [Unit Testing Library]
3. JUnit [Unit Testing Library]
4. Apache Commons [General-Purpose Library]
5. Google Guava [General-Purpose Library]
6. Jackson [JSON Parsing Library]
7. HttpClient [HTTP Library]
8. Log4j 2 [Logging Library]
9. DBCP [Database Connection Pool Library]
10. JAXB [XML Parsing Library]