I realized that the patch which I had submitted quite some time ago by email has never been incorporated into JDEE. The thing is that with my French locale + JDK1.6_20 the non-breakable space is used as a digit separator. Things are a bit more complex because in addition to that the comint output is a multibyte string.
The file version which I use is $Id: jde-jdb.el 175 2009-12-24 02:59:33Z lenbok $, and I attached a patch file. Hopefully I did not break anything while adding a new debugger class.