在實際應用中，有時候需要多個線程同時工作以完成同一件事情，而且在完成過程中，往往會等待其他線程都完成某一階段后再執(zhí)行，等所有線程都到達某一個階段后再統(tǒng)一執(zhí)行。
比如有幾個旅行團需要途經(jīng)深圳、廣州、韶關、長沙最后到達武漢。旅行團中有自駕游的，有徒步的，有乘坐旅游大巴的；這些旅行團同時出發(fā)，并且每到一個目的地，都要等待其他旅行團到達此地后再同時出發(fā)，直到都到達終點站武漢。
這時候CyclicBarrier就可以派上用場。CyclicBarrier最重要的屬性就是參與者個數(shù)，另外最要方法是await()。當所有線程都調用了await()后，就表示這些線程都可以繼續(xù)執(zhí)行，否則就會等待。
package concurrent;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class TestCyclicBarrier {
// 徒步需要的時間: Shenzhen, Guangzhou, Shaoguan, Changsha, Wuhan
private static int[] timeWalk = { 5, 8, 15, 15, 10 };
// 自駕游
private static int[] timeSelf = { 1, 3, 4, 4, 5 };
// 旅游大巴
private static int[] timeBus = { 2, 4, 6, 6, 7 };
static String now() {
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss");
return sdf.format(new Date()) + ": ";
}
static class Tour implements Runnable {
private int[] times;
private CyclicBarrier barrier;
private String tourName;
public Tour(CyclicBarrier barrier, String tourName, int[] times) {
this.times = times;
this.tourName = tourName;
this.barrier = barrier;
}
public void run() {
try {
Thread.sleep(times[0] * 1000);
System.out.println(now() + tourName + " Reached Shenzhen");
barrier.await();
Thread.sleep(times[1] * 1000);
System.out.println(now() + tourName + " Reached Guangzhou");
barrier.await();
Thread.sleep(times[2] * 1000);
System.out.println(now() + tourName + " Reached Shaoguan");
barrier.await();
Thread.sleep(times[3] * 1000);
System.out.println(now() + tourName + " Reached Changsha");
barrier.await();
Thread.sleep(times[4] * 1000);
System.out.println(now() + tourName + " Reached Wuhan");
barrier.await();
} catch (InterruptedException e) {
} catch (BrokenBarrierException e) {
}
}
}
public static void main(String[] args) {
// 三個旅行團
CyclicBarrier barrier = new CyclicBarrier(3);
ExecutorService exec = Executors.newFixedThreadPool(3);
exec.submit(new Tour(barrier, "WalkTour", timeWalk));
exec.submit(new Tour(barrier, "SelfTour", timeSelf));
exec.submit(new Tour(barrier, "BusTour", timeBus));
exec.shutdown();
}
} |
運行結果： 00:02:25: SelfTour Reached Shenzhen 00:02:25: BusTour Reached Shenzhen 00:02:27: WalkTour Reached Shenzhen 00:02:30: SelfTour Reached Guangzhou 00:02:31: BusTour Reached Guangzhou 00:02:35: WalkTour Reached Guangzhou 00:02:39: SelfTour Reached Shaoguan 00:02:41: BusTour Reached Shaoguan
|
