Storing C++ data in an instance field using CNI?

[Stanley Brown]

I played a little bit with RawData.  Soon my Java code became very GCJ 
dependent.  I eventually switched back to JNI (which GCJ handles just 
fine) storing pointers in long instance variables and NIO buffers.  To 
be fair this was mainly because I ran into complications on the Win32 
port where (1) I could not mix C++ and GCJ and (2) creating instances of 
Calendar overloaded the memory.

Could someone please explain the advantage of using RawData over the 
methods I employed?