Weird problem using Threads

From: Poochie (poochie2NO_SPAM_at_libero.it)
Date: 06/27/04

  • Next message: nobody: "Re: Help: SHA-1 problem, requires some expert advice." 
    Date: Sun, 27 Jun 2004 15:59:23 GMT

    It's a bit hard to try to explain what appens with my program, but I'll
    try:

    We have a checkers game, and the problem is when I have the CPU playing
    against itself

    >From a Menu Item I set the game mode to CPU vs CPU.

    Then I start a new game wich sets up the board and then it calls
    ProcessUpcomingMove() which is called after any change (new game or move)
    is done to the current game.

    What the program does, in CPU vs CPU, is call ProcessUpcomingMove(), this
    will have the program itself select a move from a JList that contains all
    the legal moves and then call the event of the "make move button", wich
    applies the changes and recursively calls the ProcessUpcomingMove(). Of
    course in CPU vs CPU it'll end only after the game is over.

    Currently the code which selects the move for the computer is in
    ProcessUpcomingMove() and it just works very fine, never had an error of
    any kind. The problem, of course, is that until the game between the
    machine and itself is over, the GUI of the program is stuck as its thread
    is busy doing the moves.

    So, I thought, I should have another thread doing the ProcessUpcomingMove()
    work, and then the GUI will still work and I'll be able to change game mode
    (player vs player for example) while the computer is playing against
    itself. So I amde a new class, which gets the class of
    ProcessUpcomingMove() as a parameter and does exactly what
    ProcessUpcomingMove() did before, I cut the code from there and pasted in
    the new class and I should say it would work. The WEIRD problem is that,
    seldom and at random, I get a

    java.lang.ArrayIndexOutOfBoundsException: 6 >= 1

    or similar in a DefaultListModel variable, which is related to the JList
    containing the moves.

    What I know for sure is that the code which selects a move from there never
    gets out of bounds (as without threads it does work)... the code of
    ProcessUpcomingMove() with no thread was like:

            see whose turn it is and if the set mode needs so, select a move...;
            click on the make_move_button;

    After the thread issue it's:
            
            Thread t1 = new Thread(new ProcessMoveThread(this));
            t1.start();

            Where ProcessMoveThread does:

              see whose turn it is and if the set mode needs so, select a move...;
              click on the make_move_button;

    Indipendently from getting or not the random exception, the game itself
    will seem normal scrolling though the moves history (no weird moves or one
    side moving twice in a row...) but I don't get the point of these
    exceptions it seems like something related to the recursive self call of
    ProcessUpcomingMove() but I got no clue.

    Last try:

    if I modify the threaded ProcessUpcomingMove() code to this:
            Thread t1 = new Thread(new ProcessMoveThread(this));
            t1.start();
            try {t1.join();}
            catch(InterruptedException e) {}
            click on the make_move_button; //(of couse putting this here means I
    removed it from the ProcessMoveThread)

    Well, now it dows work with absolutely no exception, but the thread is
    usless ans the GUI will obviously get stuck again due to the join()
    command.

    Any hint?

    Hoping that this get understandable,

    Poochieİ

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