A Java Interop developer focuses on enabling interoperability between Java and other programming languages or systems. They design, develop, and implement solutions that allow Java programs to interact seamlessly with non-Java components. This typically involves using Java Native Interface (JNI) or other interop frameworks to bridge the gap between different coding languages. They ensure that data types and function calls are correctly translated between systems. Their work is critical in creating efficient, scalable, and robust systems where various components, written in different languages, need to work together. They also test and debug interop issues, ensuring smooth operation.