BugSeeker for Java 2, a debugger for Java applications.

BugSeeker is a fully portable Java debugger application based on
JPDA. While it only runs on JDK 1.2 or higher, it supports
debugging JDK 1.1 and 1.0 applications too. The BugSeeker
application is a Swing-based application that allows you to step
through your program while watching threads, variables, field
values, etc.

WWW: http://www.karmira.com/products/bugseeker2/