There is a new debugger which allows to travel in time: chronon.
Chronon will record every line of code executed in a Java program along with all the variable values and exceptions, etc. and allow to browse the timeline. You can see all the exceptions that were ever thrown, select them, go back in time to see how they happened.
No breakpoints – instead you jump directly to the point in time when your code passed a line.
The demo looked pretty promising. I’m just unsure how it fares with a big code base where even simple tasks can execute millions lines of code.
Dark Views 
The number of lines of code really do not affect Chronon performance, as described here.
Performance depends on the ‘amount of execution’ recorded. A ten line program with a tight loop can sometimes have a bigger effect on performance than a million line program which spends most of its time waiting for IO
Thanks for the info.
I tried Chronon but when I use the new launch button (for example to run JUnit tests), the JUnit view clears (so something happens) but no Java VM is started. Any idea?
Are you using the latest beta (v 1.0.1.106)
http://eblog.chrononsystems.com/beta-update
Do you see anything in the ‘error log’ view?