Rankings

Caffeine: Java's de-facto in-process cache library, backed by near-optimal eviction algorithms

Neo4j: the established graph database powering production knowledge graphs and connected-data workloads at scale

Quarkus brings fast startup and low memory Java to containers and Kubernetes workloads

Mockito: The de facto Java mocking framework powering unit tests across the JVM ecosystem

Trino: mature distributed SQL engine powering analytics across heterogeneous data sources at scale

jsoup: The Java ecosystem's go-to HTML parser, now in active development after 16 years

JJWT is the de-facto Java JWT library with full JOSE spec coverage and 12 years of production use

Clojure: a mature, actively maintained Lisp on the JVM with a stable production user base

RxAndroid bridges RxJava's reactive programming model to Android's main-thread scheduler

ip2region: offline IP geolocation library with microsecond-level query speed and broad language support

Spring Cloud Alibaba full-stack scaffold for Chinese enterprise backend systems with RBAC, multi-tenancy, and 15+ business modules

ANTLR4: The established parser generator powering language tooling across 10 runtimes

Sa-Token: A lightweight all-in-one Java authentication framework built for Spring ecosystems, popular in Chinese open source community

Java algorithms reference repo with video explanations, 18K+ stars and active maintenance

IK Analyzer brings Chinese word segmentation to Elasticsearch and OpenSearch with customizable dictionaries

JustAuth: Java library unifying OAuth login for 40+ Chinese and global platforms in a single API

Zipkin: Mature distributed tracing system with 13+ years of production use

MyBatis-Plus: The de-facto CRUD extension layer for Java Spring applications in the Chinese enterprise ecosystem

Chinese-language Java learning guide with 17K stars, targeting students and job seekers preparing for technical interviews

QuestDB: High-throughput time-series database targeting financial and IoT workloads with SQL