Worked on the alibaba/fastjson2 repository to enhance the correctness and stability of JSON serialization in Java applications. Focused on resolving two critical bugs, including ensuring that the ToStringSerializer is properly applied to Integer and Long types, which improves predictable string representations and client interoperability. Addressed a capacity issue in JSONWriterUTF8.writeStringEscaped by adjusting buffer allocation to better handle escaped characters, thereby reducing potential runtime errors. Employed targeted unit testing and regression tests to verify these fixes, increasing test coverage and minimizing the risk of future regressions. Demonstrated strong skills in Java development, JSON processing, and systematic bug fixing.