Fastjson

Optimized as one of the fastest JSON libraries for Java, with benchmarks showing superior speed on server-side and Android, as highlighted in the project goals and linked benchmark tests.

Provides straightforward methods like toJSONString() and parseObject() for easy JSON conversion, making it accessible without complex configurations.

Supports serialization and deserialization of arbitrary Java objects, including those with deep inheritance hierarchies and extensive generics, as stated in the documentation.

Can work with pre-existing Java objects without requiring source code modifications, enabling integration into legacy systems.