alibaba/fastjson ? reverse-engineered prompt

Build me a Java library that can turn objects into JSON and JSON back into Java objects, with a big focus on speed and safety.

I want a simple API that feels easy to use, something like toJSONString and parseObject, and it should work with normal Java objects, even ones I did not design myself. Please support nested objects, inheritance, generic types, lists, maps, and custom object formatting. It should be solid enough for server use, but also work well on Android.

Please include good tests, a couple of realistic examples, and benchmark friendly code so I can see it is fast. If you need to check current best practices or docs online while building it, go ahead. Make the project clean, reliable, and ready to publish as a reusable library.