Top 10 Must‑Star Java GitHub Projects Every Backend Engineer Should Know

1. CS-Notes

Stars: 92.1k. Covers interview fundamentals, LeetCode, operating systems, computer networks, system design, Java, Python, C++. URL: https://cyc2018.github.io/CS-Notes

Includes algorithms (剑指 Offer, LeetCode), databases (SQL, MySQL, Redis), Java basics, containers, concurrency, JVM, I/O, system design basics, distributed systems, caching, message queues.

2. JavaGuide

Stars: 69.8k. A comprehensive Java learning and interview guide. URL: https://github.com/Snailclimb/JavaGuide (also on Gitee).

Key sections: Java memory areas, JVM garbage collection, monitoring tools, class file structure, class loading process, class loaders, JVM parameters guide, GC tuning strategies, JVM overview.

3. java-design-patterns

Stars: 55.6k. Design patterns implemented in Java. URL: https://github.com/iluwatar/java-design-patterns. Essential for architects and developers to improve code readability and interview preparation.

4. elasticsearch

Stars: 47.2k. Open‑source distributed search engine based on RESTful design. URL: https://github.com/elastic/elasticsearch.

5. SpringBoot

Stars: 45.7k. Spring Boot project (no description on GitHub page). URL: https://github.com/spring-projects/spring-boot. Core of Spring Cloud micro‑service ecosystem and a revolution for Java enterprise development.

6. interviews

Stars: 42.2k. Everything you need to know about job hunting. URL: https://github.com/kdn251/interviews. Includes algorithm resources and interview tips.

7. RxJava

Stars: 41.9k. Reactive programming extension for the JVM, providing asynchronous and event‑driven capabilities. URL: https://github.com/ReactiveX/RxJava.

8. advanced-java

Stars: 39.3k. Comprehensive guide for advanced Java engineers covering high concurrency, distributed systems, high availability, micro‑services, massive data processing, and database sharding strategies.

9. okhttp

Stars: 36k. Square’s HTTP client for Java and Kotlin, used in Android and server‑side projects. URL: https://github.com/square/okhttp.

10. guava

Stars: 36k. Google core libraries for Java, offering new collection types, immutable collections, graph library, concurrency utilities, I/O, hashing, caching, and rate limiting. URL: https://github.com/google/guava.

Conclusion

These top‑starred Java‑related GitHub projects demonstrate the vibrant open‑source ecosystem, with several led by Chinese developers. While many are curated knowledge bases, projects like Elasticsearch and SpringBoot have far greater impact on the industry.

Among the most influential domestic projects is Dubbo (https://github.com/apache/dubbo).