Java: How could a breakpoint stop an applet from painting without *ever being tripped*?

Question

In eclipse I am writing some code that crawls a specific webpage and downloads an applet, which it then adds to a JFrame and executes. If I run program without adding any breakpoints, it works perfectly. It loads the applet, and it begins running. However, if I add a breakpoint to the applets update(Graphics g) method, it simply stops refreshing. This is expected, obviously, but it never actually trips the breakpoint.

I know breakpoints are working in general with my setup, and in fact if I add a breakpoint to the paint(Graphics g) method of the exact same applet, it will trip whenever you would expect it to.

The only thing that is slightly unconventional about this is that I don't have the source of the applet which I am displaying. Instead, I simply set a breakpoint on the method entry.

If I disable the breakpoint while the applet is running, it resumes painting, but if I enable it again, it won't always stop repainting.

I don't know if this could somehow be the expected behavior of eclipse/jvm, or if I have found a bug. If it is a bug, is it a bug in eclipse or the jvm?

Answer 1

Just a suggestion: could you check what version of the JVM you are executing your applet with?

There were mentions of troubles with breakpoints (also detailed here) and the latest jdk6.0_u14,
so if you are using this version, you may want to check if the same behavior is observed with 6.0_u13.

Answer 2

Have a look at the debug panel showing your threads. It might well be another thread than you expect that breaks on the breakpoint.