Java多线程之线程并发库的其他同步工具类
CyclicBarrier
表示大家彼此等待，大家集合好后才开始出发，分散活动后又在指定地点集合碰面，这就好比整个公司的人员利用周末时间集体郊游一样，先各自从家出发到公司集合后，再同时出发到公园游玩，在指定地点集合后再同时开始就餐，…
package javaplay.thread.test;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class CyclicBarrierTest {
public static void main(String[] args) {
ExecutorService service = Executors.newCachedThreadPool();
final CyclicBarrier cb = new CyclicBarrier(3);// 3表示当有3个线程同时到达了才能继续向下走
for (int i = 0; i < 5; i++) {
Runnable runnable = new Runnable() {
public void run() {
try {
Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程" + Thread.currentThread().getName() + "即将到达集合地点1，当前已有" + (cb.getNumberWaiting() + 1) + "个已经到达，" + (cb.getNumberWaiting() == 2 ? "都到齐了，继续走啊" : "正在等候"));
cb.await();
Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程" + Thread.currentThread().getName() + "即将到达集合地点2，当前已有" + (cb.getNumberWaiting() + 1) + "个已经到达，" + (cb.getNumberWaiting() == 2 ? "都到齐了，继续走啊" : "正在等候"));
cb.await();
Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程" + Thread.currentThread().getName() + "即将到达集合地点3，当前已有" + (cb.getNumberWaiting() + 1) + "个已经到达，" + (cb.getNumberWaiting() == 2 ? "都到齐了，继续走啊" : "正在等候"));
cb.await();
} catch (Exception e) {
e.printStackTrace();
}
}
};
service.execute(runnable);
}
service.shutdown();
}
}
CountDownLatch
犹如倒计时计数器，调用CountDownLatch对象的countDown方法就将计数器减1，当计数到达0时，则所有等待者或单个等待者开始执行。
可以实现一个人（也可以是多个人）等待其他所有人都来通知他，这犹如一个计划需要多个领导都签字后才能继续向下实施。还可以实现一个人通知多个人的效果，类似裁判一声口令，运动员同时开始奔跑。
用这个功能做百米赛跑的游戏程 序不错哦！
package javaplay.thread.test;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class CountdownLatchTest {
public static void main(String[] args) {
ExecutorService service = Executors.newCachedThreadPool();
final CountDownLatch cdOrder = new CountDownLatch(1);// 吹口哨的 一吹大家才能跑
final CountDownLatch cdAnswer = new CountDownLatch(3);// 等待结果的 大家都到了
// 结果才出来
for (int i = 0; i < 3; i++) {
Runnable runnable = new Runnable() {
public void run() {
try {
System.out.println("线程" + Thread.currentThread().getName() + "正准备接受命令");
cdOrder.await();// * 等待归0才开始执行
System.out.println("线程" + Thread.currentThread().getName() + "已接受命令");
Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程" + Thread.currentThread().getName() + "回应命令处理结果");
cdAnswer.countDown();
} catch (Exception e) {
e.printStackTrace();
}
}
};
service.execute(runnable);
}
try {
Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程" + Thread.currentThread().getName() + "即将发布命令");
cdOrder.countDown();// 初始为1 一countDown就变为0 则停在*的代码开始执行
System.out.println("线程" + Thread.currentThread().getName() + "已发送命令，正在等待结果");
cdAnswer.await();
System.out.println("线程" + Thread.currentThread().getName() + "已收到所有响应结果");
} catch (Exception e) {
e.printStackTrace();
}
service.shutdown();
}
}
Exchanger
用于实现两个人之间的数据交换，每个人在完成一定的事务后想与对方交换数据，第一个先拿出数据的人将一直等待第二个人拿着数据到来时，才能彼此交换数据。
A线程有数据1,它需要与B线程的数据2做交换
B线程有数据2,它需要与A线程的数据1做交换
那么什么时候交换呢?得等AB都做好准备才行。
package javaplay.thread.test;
import java.util.concurrent.Exchanger;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
public class ExchangerTest {
public static void main(String[] args) {
ExecutorService service = Executors.newCachedThreadPool();
final Exchanger<String> exchanger = new Exchanger<String>();
service.execute(new Runnable() {
public void run() {
try {
String data1 = "zxx";
System.out.println("线程" + Thread.currentThread().getName() + "正在把数据" + data1 + "换出去");
Thread.sleep((long) (Math.random() * 10000));
String data2 = (String) exchanger.exchange(data1);
System.out.println("线程" + Thread.currentThread().getName() + "换回的数据为" + data2);
} catch (Exception e) {
}
}
});
service.execute(new Runnable() {
public void run() {
try {
String data1 = "lhm";
System.out.println("线程" + Thread.currentThread().getName() + "正在把数据" + data1 + "换出去");
Thread.sleep((long) (Math.random() * 10000));
String data2 = (String) exchanger.exchange(data1);
System.out.println("线程" + Thread.currentThread().getName() + "换回的数据为" + data2);
} catch (Exception e) {
}
}
});
}
}
