The keyword "native" means that the implementation is NOT in Java. I would guess it's written in C or C++. As for the answer to your question, I'm not sure where you find the implementation. Perhaps look for an Object.c or Object.cpp file in the source distribution? I've never looked at the source myself, so that's only a guess. I've never worked with native methods, either, so I'm not entirely sure about the details about how the Java source interacts with the native source in C/C++.