java - 线程对象不同步

Question

所以我编写了这个程序来运行这个机器人类的多个线程，使用 cyclobarrier 来同步线程。由于我对 cyclobarrier 知之甚少，我认为它会自动同步我的线程，但似乎不会。我需要做什么才能让我的机器人线程根据我的进度整数值进行同步？

public class Robot implements Runnable{
public static final int on = 0x0001;
public static final int clockwise = 0x0002;
public static final int counter = 0x0004;
int  opcode;
int moveCount = 0;
int rotation, increment, progress = 0;
boolean CW;

ProgressBar prgBar;
CyclicBarrier cyclicBarrier;
Controller c;
Motor m;

public Robot(CyclicBarrier cyclicBarrier, Motor m)
{
    opcode = 0;
    this.cyclicBarrier = cyclicBarrier;
    this.m = m;
}




public void run(){
    System.out.println("Running: ");

    try {
        while(progress <= 24){
            i = m.Engage(this, i, increment/4);
            prgBar.setProgress(this, progress);
        }
        System.out.println("Sleeping: ");
        Thread.sleep(3000);
        System.out.println(Thread.currentThread().getName()+ " waiting at barrier 1");
        cyclicBarrier.await();

        while(progress <= 49){
            i = m.Engage(this, i, increment/2);
            prgBar.setProgress(this, progress);
        }
        System.out.println("Sleeping: ");
        Thread.sleep(3000);
        System.out.println(Thread.currentThread().getName()+ " waiting at barrier 2");
        cyclicBarrier.await();

        while(progress <= 74){
            i = m.Engage(this, i, ((increment/4)*3));
            prgBar.setProgress(this, progress);
        }
        System.out.println("Sleeping: ");
        Thread.sleep(3000);
        System.out.println(Thread.currentThread().getName()+ " waiting at barrier 3");
        cyclicBarrier.await();

        while(progress <= 99){
            i = m.Engage(this, i, increment);
            prgBar.setProgress(this, progress);
        }
        System.out.println("Sleeping: ");
        Thread.sleep(3000);
        System.out.println(Thread.currentThread().getName()+ " waiting at barrier 4");
        cyclicBarrier.await();

    } catch (Exception e){
        e.printStackTrace();
    }
    prgBar.setProgress(this, progress);
    System.out.println("Engaging: ");
}

公共(public)类 Controller {

public static void main(String[] args){
    CyclicBarrier cyclicBarrier = new CyclicBarrier(4);
    Motor m = new Motor();


    Robot xRob = new Robot(cyclicBarrier, m);
    Robot yRob = new Robot(cyclicBarrier, m);
    Robot zRob = new Robot(cyclicBarrier, m);

    Thread xRobThread = new Thread(xRob);
    Thread yRobThread = new Thread(yRob);
    Thread zRobThread = new Thread(zRob);

    boolean clockwise = true, counterClockwise = false;




    m.setMotor(clockwise, 14400, xRob);
    m.setMotor(clockwise, 7200, yRob);
    m.setMotor(counterClockwise, 28800, zRob);

    xRobThread.start();
    yRobThread.start();
    zRobThread.start();

    try {
        xRobThread.join();
        yRobThread.join();
        zRobThread.join();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }


    System.out.printf("x = %d y = %d z = %d\n\n", xRob.moveCount, yRob.moveCount, zRob.moveCount);

}
}

Answer 1

程序运行时会做什么？您期望它做什么？ (即，您认为“同步我的线程”是什么意思？)

至少，您的更新现在包含足够的信息供我猜测，并且我猜测程序挂起。您的 main() 例程为四方创建一个新的 CyclicBarrier，然后创建三个线程。每个线程都调用 cycloBarrier.await()，但我没有看到任何第四方。在四个线程调用await() 之前，屏障不会打开。

<小时/>

其他信息:

好吧，假设您有一个循环可以取得某种“进展”。您可以通过执行以下操作，让第一个达到特定进度阈值的线程等待其他线程 catch :

double progress = 0.0;
static final double CHECKPOINT = 0.5;
static final double FINISHED = 1.0;
boolean reachedCheckpoint = false;

while (progress < FINISHED) {
    progress = makeSomeProgress();
    if (! reachedCheckpoint && progress >= CHECKPOINT) {
        cyclicBarrier.await();
        reachedCheckpoint = true;
    }
}

显然，如果你想要有多个检查点，程序会稍微复杂一些，但这就是基本思想。请记住，为其构造 CyclicBarrier 的“各方”数量必须完全等于实际使用它的线程数量。