Worked on the uber/NullAway repository to enhance static analysis for Java code by improving nullability handling in common string operations. Developed a feature that enables NullAway to recognize and correctly analyze java.util.Objects.toString(Object, String) when the default value may be null, addressing a subtle source of potential null pointer exceptions. The implementation involved Java development, static analysis techniques, and unit testing, with targeted tests validating both null and non-null default scenarios. This work increased the reliability of nullability analysis, guiding developers toward safer code patterns and reducing the risk of dereferencing errors in Java applications using this static analysis tool.