JNI allows the use of function libraries made in languages such as C, C++, VB from Java applications. The advantage of JNI is that you don't need to write the calling function definition in Java ...

Currently Java objects have a 128-bit object header in the 64-bit HotSpot VM, with a 64-bit multipurpose header word and a 64-bit class pointer. With average object sizes of five to six words, ...