How can you have a "light" version of Java and still call it Java? It has to implement the Java specification, so it's going to be fairly non-trivial. That said, there is GCJ/libgcj, which is open-source and not fully JDK 1.4 compliant, so it may be your best bet.
If you want to see some of the implementation details, go into your Java installation folder and find the file called src.zip or similar. Unzip that and explore it; you will find the code for all the well-known Java API classes in there.
This is what I wast looking at: C:\Program Files\Java\jdk1.5.0_12\include\jvmdi.h I don't know that such is actually what the poster is looking for but the header really looks to me like something that would explain some general operating principles. EG:
RE: Originally posted by Campbell Ritchie:
I have never seen these C style headers, Nicholas. You have no idea where they are?
And thus would address Original Poster's JVM is implemented by c/c++ or at least it does that for me. I am not degreed in cs so let's split some nuances before getting head-on in determining what OP is looking for.
"The differential equations that describe dynamic interactions of power generators are similar to that of the gravitational interplay among celestial bodies, which is chaotic in nature."
Those headers are indeed for folks working with the JNI -- you use the headers to write C/C++ code that plugs into the JVM to implement native methods, or to invoke the JVM from a C/C++ program of your own devising. They give precisely zero insight into the implementation of a JVM, since JNI is an implementation-indendent interface standard.
In any case, there's really no such thing as a "simple JVM implementation" -- it's a complicated thing. Instead, what you should be looking for is a good explanation of how the JVM works and how it might be implemented. There's the Java VM specification, available as a free download from Sun, which tells you everything a JVM is supposed to do; and there are a number of other books out there that try to give you an idea of how the JVM works.