How can I dump log messages from Java code in Firefox extension?

Hi,

I can call a Java code I wrote from a Firefox extension written in
JavaScrpit, using the workaround described at:
https://developer.mozilla.org/en/Java_in_Firefox_Extensions

But when I try to dump some debug messages by using Logger or
System.out, nothing appears in the console of Firefox.
What is a good way of recording log messages in JavaCode that is
called from a Firefox extension?

Just to be clear, what I mean by the console is the command-line
window that shows up when you invoke firefox.exe with the "-console"
option.
I changed the value of "browser.dom.window.dump.enabled"  to true, and
I can successfully log messages by dump() in JavaScript code.

Sachiko