Re: TimerTask not work as expected

Lew <>
Tue, 18 Jan 2011 08:49:14 -0500
On 01/17/2011 11:54 PM, SamuelXiao wrote:

On Jan 13, 4:06 am, Travers<> wrote:

I don't think you understand the Java API you are using. You will not get the results you want until you understand what you are playing with.

Timer() spawns a thread and returns _instantly_ thus btnRoll() ends before the TimerTask is even executed. Timer is not "synchronous"--it does not wait for the tasks to finish.

But I also think you have structured your program poorly. For event-driven GUI programs, especially games, you have to give up "Do A then do B" structure.

But if you want to make sure btnRoll()'s Timer task thread finishes first, you should add code in btnRoll to _wait_ for the Timer task to finish.

Thanks for your help, I think I have solved the synchronous problem. I
have added an Object lock to do the syn.

    public void btnRoll(){
        final Timer timer = new Timer();
        final int index = turn - 1;
        boolean snakeEyes = false;
        dice1 = (int)(Math.random() * 6 + 1);
        dice2 = (int)(Math.random() * 6 + 1);

        if(dice1 == dice2) {
            snakeEyes = true;
            rolled = false;

        if(snakeEyes == true){
            tempFlagPlayer = true;
            tempFlagPlayer = false;

        timer.schedule(new TimerTask(){
            private int diceSum = dice1 + dice2;

            public void run(){
                synchronized(lock) {
                    if (diceSum> 0){
                        movePlayer(players.get(index), tempFlagPlayer); // move player
one space each time
                        diceSum --;
                        rolled = true;
        }, 100L,100L);

and in AIturn(int tempNumOfPlayers){

public void AIturn(int tempNumOfPlayers){
      synchronized(lock) {
      catch(InterruptedException e){}
[0] == 0){"enter btnBuy()");
         if(rolled) {

but I found there is another problem for AIturn(int tempNumOfPlayers),
in the btnRoll() in AIturn(),

if (diceSum> 0){
        movePlayer(players.get(index), tempFlagPlayer); // move player one
space each time
        diceSum --;

I found the repaint() doesn't work when it comes to AIturn() call, is
it repaint must be triggered by ActionListener component? If there any
way to force repaint()? Thanks.

Dude, that is just horrid code.

The idea with critical sections (parts that share data between threads) is to
keep them short and not do much inside them.

What data are you protecting with the lock?

I don't see any shared data that is completely guarded. That's fatal right there.

At least 'repaint()' is one of those methods that you can safely call outside
the EDT. Did you know that?


You might not need to call 'repaint()' explicitly. I'd be surprised if you do.

Don't use 'wait()/notify()' at all.

You truly need to study concurrent Java programming. "Throw enough shit at
the wall and some of it will stick" is not good programming.

Ceci n'est pas une pipe.

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