First, read the JVM specification: http://java.sun.com/docs/books/jvms/

On Wed, 12 Dec 2007 02:10:32 -0800 (PST), Jagadesh
<mca.jagadesh@gmail.com> wrote, quoted or indirectly quoted someone
who said :

see http://mindprod.com/jgloss/jvm.html

The work is not the JVM proper.  It should be not that much harder
than writing a FORTH interpreter.  The problem is writing all the
native methods, especially for the GUI.  You should be able to write a
JVM with some primitive IO, at least enough to run some
console-mode arithmetic programs.

You need to learn about:
- the JVM specification
- VM technology
- GC technology
- architecture of processors you want to support
(and that is *not* counting what you need to provide the
runtime library)

It should be doable to create a toy JVM. You will not
be able to create a serious JVM alone for the simple
reasons that it will take more man years than
a single person can hope to live.

Arne