Java continuations with joeq

[Christopher Oliver]

I recently took a look at joeq (http://joeq.sourceforge.net/) which is a 
Java virtual machine written in Java. Included is a "reflective" Java 
interpreter that can run on top of an existing Java virtual machine 
(e.g. Sun JRE). It can interpret class files, but can also delegate some 
(or all) method calls to the underlying VM as well. It looks like it 
would be quite easy to support Java language continuations with this 
interpreter. There are some drawbacks however:

1) In order to be included in a continuation a method call must be 
interpreted by joeq - not by the underlying VM (= severe performance 
penalty. Probably at least 15 to 20 times slower than hotspot compiled 
code). Although the joeq interpeter is very high quality, I did some 
informal tests and it appears to actually be slower than interpreted 
Rhino (not sure exactly why, perhaps because Rhino bytecodes are higher 
level), but was significantly faster than BeanShell (which  is a Java 
source code interpreter).
2) It has an LGPL license.

Chris