On Windows, the basic Java Integer types are defined as long and __int64 respectively. In particular, the former is rather problematic since it breaks compilation as the Visual C++ becomes stricter and more compliant with every release, which means the way Windows code treats long as a typedef for int is no longer correct, especially with -permissive- enabled. Instead of changing every piece of broken code to match the jint = long typedef, which is far too time consuming, we can instead change jint to an int (which is still the same 32 bit number type as long), as there are far fewer problems caused by this definition. It's better to get this over and done with sooner than later when a future version of Visual C++ finally starts to break on existing code