可同时执行指定数量的任务

  1. /**
  2.  * 可同时执行指定数量的任务
  3.  *
  4.  * @author wujianchuan 2020/9/29 11:43
  5.  */
  6. public class ParallelLock {
  8.     private final Sync sync;
  10.     public ParallelLock(int parallelThreadCount) {
  11.         sync = new Sync(parallelThreadCount);
  12.     }
  14.     static final class Sync extends AbstractQueuedSynchronizer {
  16.         private static final long serialVersionUID = 8083049666357266306L;
  18.         Sync(int count) {
  19.             setState(count);
  20.         }
  22.         @Override
  23.         protected int tryAcquireShared(int arg) {
  24.             for (; ; ) {
  25.                 int count = getState();
  26.                 int newCount = count - arg;
  27.                 //NOTE: 小于0获取同步状态失败
  28.                 if (newCount < 0 || compareAndSetState(count, newCount)) {
  29.                     return newCount;
  30.                 }
  31.             }
  32.         }
  34.         @Override
  35.         protected boolean tryReleaseShared(int arg) {
  36.             for (; ; ) {
  37.                 int count = getState();
  38.                 int newCount = arg + count;
  39.                 if (compareAndSetState(count, newCount)) {
  40.                     return true;
  41.                 }
  42.             }
  43.         }
  44.     }
  46.     public void lock() {
  47.         sync.acquireShared(1);
  48.     }
  50.     public void unlock() {
  51.         sync.releaseShared(1);
  52.     }
  53. }