Demonstration of mixing Java code with C++ code (the Java Native Interface). Well, the applet does not work from Mozilla.

But here is all the code:

GUI.java (the applet, shows all the results)
native.c (the C code: the computable functions)
Makefile (the Makefile)
gui.html (use appletviewer gui.html)

Additionally, here is some documentation:

JNI include
JNI Types

To run: type make, then type appletviewer gui.html