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@@ -1,7 +1,6 @@
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### jdk并发包里常用的类
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----
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-
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+---
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* ConcurrentHashMap
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@@ -19,13 +18,90 @@
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* CountdownLatch
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+ 闭锁，确保一个服务不会开始，直到它依赖的其他服务都已近开始，它允许一个或多个线程，等待一个事件集的发生。
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通过减计数的方式，控制多个线程同时开始某个动作。当计数为0时，await后的代码才会被执行。
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提供await（）和countDown（）两个方法。
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* CyclicBarrier
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- 与countDownLatch不同，cyclicBarrier是当await的数量达到了设定的数量后，才继续往下执行。
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-await方法首先进行加锁操作，然后对count属性执行减1操作，如果减后的值等于0，则执行传入的Runnable对象。
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+ cyclicBarrier中的await方法会对count值减1，并阻塞当前线程，直到直到count==0时先调用CyclicBarrier内部的Runnable任务，然后当前线程才继续往下执行，然后进入下一轮循环。
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+
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+ 与CountdownLatch不同的是，它可以循环重用。
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+
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+```
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+import java.util.concurrent.CyclicBarrier;
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+
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+public class TestCyclicBarrier {
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+
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+ private static final int THREAD_NUM = 5;
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+
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+ public static class WorkerThread implements Runnable {
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+
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+ CyclicBarrier barrier;
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+
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+ public WorkerThread(CyclicBarrier b){
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+ this.barrier = b;
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+ }
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+
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+ @Override
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+ public void run() {
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+ try {
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+ System.out.println("Worker's waiting");
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+ // 线程在这里等待，直到所有线程都到达barrier。
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+ barrier.await();
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+ System.out.println("ID:" + Thread.currentThread().getId() + " Working");
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+ } catch (Exception e) {
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+ e.printStackTrace();
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+ }
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+ }
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+
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+ }
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+
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+ public static void main(String[] args) {
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+ CyclicBarrier cb = new CyclicBarrier(THREAD_NUM, new Runnable() {
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+
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+ // 当所有线程到达barrier时执行
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+ @Override
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+ public void run() {
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+ System.out.println("Inside Barrier");
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+ }
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+ });
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+
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+ for (int i = 0; i < 10; i++) {
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+ new Thread(new WorkerThread(cb)).start();
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+ }
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+ }
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+
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+}
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+```
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+结果：
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+
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+```
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+Worker's waiting
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+Worker's waiting
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+Worker's waiting
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+Worker's waiting
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+Worker's waiting
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+Inside Barrier
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+ID:13 Working
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+ID:9 Working
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+ID:12 Working
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+ID:11 Working
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+ID:10 Working
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+Worker's waiting
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+Worker's waiting
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+Worker's waiting
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+Worker's waiting
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+Worker's waiting
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+Inside Barrier
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+ID:18 Working
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+ID:14 Working
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+ID:16 Working
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+ID:15 Working
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+ID:17 Working
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+
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+```
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+
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* AtomicInteger
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@@ -87,3 +163,8 @@ WriteLock writeLock=lock.writeLock();
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ReadLock readLock=lock.readLock();
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《分布式java应用》P165
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+
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+#### 汇总
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+
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+
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+
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wenwan
