Eclipse Debugging Error: ClassNotFoundException

I just hit a really annoying (sort of) bug in Eclipse. I could not debug any of my projects because they immediately stopped with a call stack like the following:

terrain.TerrainApp at localhost:49827   
    Thread [main] (Suspended (exception ClassNotFoundException))   
        ClassLoader.findBootstrapClass(String) line: not available [native method]   
        Launcher$ExtClassLoader(ClassLoader).findBootstrapClass0(String) line: not available   
        Launcher$ExtClassLoader(ClassLoader).loadClass(String, boolean) line: not available   
        Launcher$AppClassLoader(ClassLoader).loadClass(String, boolean) line: not available   
        Launcher$AppClassLoader.loadClass(String, boolean) line: not available   
        Launcher$AppClassLoader(ClassLoader).loadClass(String) line: not available   
        Launcher$AppClassLoader(ClassLoader).loadClassInternal(String) line: not available

I found people with similar issues on various message boards, but no solutions.

Then I figured out that if I kept hitting continue (to go past the breakpoint) it would eventually reach my actual application. Along the way though, java was triggering ClassNotFoundExceptions for every single class referenced in my code, which was causing Eclipse to break. It turns out that these ClassNotFoundExceptions are normal behavior – they are supposed to happen for every new class, but having eclipse set a breakpoint for each one is definitely not!

To solve the problem, I had to open up the breakpoint window and disable the breakpoint “ClassNotFoundException: caught and uncaught”  — I have no idea how this breakpoint got set in the first place, I certainly didn’t do it!

So now I can finally debug my programs without relying on tons of print statements… that should help my progress.

January 17, 2009 · Filed under Coding

44 Comments »

  1. Benny Said,

    January 28, 2009 @ 3:00 am

    Thanks a lot, You solved my problem and correctly you mention the problem is a common one yet without any proper advise (other than this one) – Chapeau again

  2. Chuck Said,

    January 29, 2009 @ 6:57 pm

    I am receiving the error but I can’t find the breakpoint “ClassNotFoundException”. Where is this located?

    If you switch to the debug perspective, there should be a window listing any breakpoints that have been set. In my case, I could disable the breakpoint there — admin

  3. Chuck Said,

    January 30, 2009 @ 3:36 am

    Ok. The only breakpoint I have set in that window is the breakpoint I set where I am instantiating a new object.

  4. Erinc Arikan Said,

    March 3, 2009 @ 10:07 am

    Thanks a lot, I spent two hours and read lots of posts about it, only solution proposed was yours and it worked.

  5. JQuimbly Said,

    April 6, 2009 @ 4:27 pm

    This was very helpful. Lesson learned: never set ‘Exception’ or ‘Throwable’ in the exceptions pane!

  6. hugh Said,

    April 13, 2009 @ 8:24 am

    Thanks for the advice. I too never set the breakpoints for ClassNotFoundException it just seemed to happen itself. Strange

  7. hui Said,

    May 8, 2009 @ 4:45 am

    thank you very much. Very helpful.

  8. AllanC Said,

    May 31, 2009 @ 8:39 am

    Ha! I use Eclipse all the time. But I just installed Ganymede and started a brand new project (which I rarely do). I kept thinking it was a classpath problem. Then I cleared all break points. I had never set any in the first place. Bingo! “Problem solved.”

  9. Nilesh Said,

    June 8, 2009 @ 12:10 pm

    Thank you very much. This is very helpful.

    Regards,
    Nil

  10. Eduardo Said,

    June 22, 2009 @ 11:09 am

    You made my day. I am not conscious of having set that breakpoint. And that is now the real question, how did that breakpoint end up in all our Eclipses?

  11. Bo Liang Chen Said,

    June 23, 2009 @ 8:14 pm

    Thanks, I also met that issue, it’s really helpful

  12. Svetlana Said,

    June 25, 2009 @ 3:02 am

    Thank you very much: so easy and so helpful!

  13. Eric Said,

    August 20, 2009 @ 8:06 pm

    Thanks, it solves the problem:)

  14. Jean Said,

    November 9, 2009 @ 2:26 pm

    Very helpful. I ran into the same problem and your suggestion was the only way to get the debugger to work again.

  15. Iman Said,

    November 15, 2009 @ 3:46 am

    Oh, Thanks a lot
    I didn’t know those error come from?!!!
    Your suggestion so helpful

  16. Thejaswini Said,

    November 30, 2009 @ 10:51 pm

    thanks……this helped me a lot…
    but the one thing i did not understand is how did these breakpoints got set??

  17. Cesare Said,

    January 19, 2010 @ 4:47 am

    Thank you!

  18. antonio Said,

    January 29, 2010 @ 12:03 pm

    Sorry, I didn’t understand.
    You say: “ClassNotFoundExceptions are normal behavior – they are supposed to happen for every new class”

    If I debug moving with F5, I get the error, with F6 not, but in this way I cannot debug new classes.

    How I can debug them?

    Thank you very much
    Antonio

  19. Emmanuel Said,

    February 16, 2010 @ 10:59 pm

    Thanks soo much. i have searched to the end of the internet looking for this answer. you rock

  20. Jan Said,

    March 8, 2010 @ 9:33 am

    Thanks a lot – you solved my problem.
    I also can’t remember having set this breakpoint, I’m almost sure I didn’t.

  21. Gaurav Said,

    March 30, 2010 @ 5:49 am

    Thanks a lot… This worked for me as well…

  22. Osvaldo Said,

    April 9, 2010 @ 11:34 am

    You are a genius!

    Thanks for save my day :)

    OOO

  23. Utpal Utkalit Said,

    April 11, 2010 @ 10:34 pm

    i have been trying to figure out the solution to this issue for past 4 days..tried many solutions but nothing worked.Hats off to you –this worked

  24. Srivigneshwar Said,

    April 15, 2010 @ 12:25 pm

    THanks a loooooooooooooooooooooooooooooot.. as I was new to eclipse IDE I unable to resolve this problem for past 3 days.. today it solved .. thanks once again ..

  25. jamie Said,

    July 12, 2010 @ 4:10 pm

    THANK YOU!!!!!!

  26. richa Said,

    July 28, 2010 @ 5:01 am

    thanks it worked!!!

  27. vilas Said,

    October 27, 2010 @ 5:17 am

    thanx a lot :)

  28. Deepak Singh Said,

    December 12, 2010 @ 9:51 pm

    Thanks Alot.

  29. Sergey Said,

    December 19, 2010 @ 3:38 am

    Thank you !!! I’ve spent a lot of time looking for fix of this annoying error!

  30. vagaraju Said,

    January 24, 2011 @ 4:48 am

    delete respective eclipse class path folder and clean and build the project….it resolve this type problems

  31. vagaraju Said,

    January 24, 2011 @ 4:51 am

    means…..delete the folder which contains classes of the your project source code(usually it’s generated by eclipse in debug mode.)

    like as shown below :

    …web\WEB-INF\classes\com….

  32. Eugene Said,

    January 24, 2011 @ 1:54 pm

    Thank you!

  33. cary Said,

    January 26, 2011 @ 10:58 pm

    good guy, it helps!

  34. Arunav Said,

    February 20, 2011 @ 10:10 am

    Thanks a lot!
    I m new to Java.
    I really spend a lot of time , this post helped me to solve the problem

  35. Prashant Pharate Said,

    March 15, 2011 @ 6:27 am

    This solved my issue as wel . Thanks budy

  36. dominic Said,

    May 6, 2011 @ 12:23 am

    thx a lot. it helps

  37. Ashok N Said,

    June 28, 2011 @ 12:05 am

    Thanks…its works for me!

  38. Jim C Said,

    August 17, 2011 @ 3:16 pm

    You are so awesome – been spending three hours snatching my hair out!!!

  39. shruti Said,

    September 13, 2011 @ 5:33 am

    Thanks a lot, solved my problem :)

  40. Mehdi Said,

    October 5, 2011 @ 10:34 am

    Wow! Thanks a lot. I was playing with this problem for two days and you just solved it :-) You saved a lot of my time.

  41. vagaraju Said,

    November 17, 2011 @ 9:47 pm

    this problem may occur with different causes..u can find the cause in elipse at following location :

    window–>show view–>Other–>Genaral–>Problems

    normally it will occur becuase of the corrupted jar files…remove the respective jar files from the path …so that it will run smothlly…

  42. Georg Said,

    November 20, 2011 @ 3:23 am

    Thank you very much!

  43. Seva Said,

    November 24, 2011 @ 6:35 am

    Thank you.

  44. Armin Said,

    December 9, 2011 @ 7:47 am

    Thanks sooooo much!!! after half a year of System.out.println(“”),
    I can debug. So great! I will suggest you for the nobel prize ;)

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