On Mon, 2006-06-05 at 16:27 +0200, Caster wrote:
> ...
> Somebody correct me if I'm wrong, but the bytecode compiled will be the
> same no matter which JDK you use. Any optimisations are done with
> run-time JIT compiling, and depends on the VM running the bytecode
> (which can be different from the VM used to compile).

I think this statement is a little too broad to be considered correct.
The compiler can (and often does) make changes to the resulting binaries
that may be VM-level specific (e.g., targeted for a 1.5 VM).  Consider
the "-target" argument for javac, for example, which "Allow[s] javac to
use 1.5 specific features in the libraries and virtual
machine" (http://java.sun.com/j2se/1.5.0/docs/relnotes/features.html ).

For more information see the following in the section labeled
"Cross-Compilation Options":

http://java.sun.com/j2se/1.5.0/docs/tooldocs/solaris/javac.html


I also found some interesting information about different bytecode
versions here:
http://alumnus.caltech.edu/~leif/opensource/bcver/BcVerTask.html

More information can be found in Sun articles referenced there.

Finally, it looks like some information appears in the following JSR
abstract:
http://www.jcp.org/en/jsr/detail?id=202

~ Greg