Countdownlatch、CyclicBarrier、join区别

1、join
模拟现在有三个worker，采用join的方法控制：

package org.pbccrc.org.pbccrc.thread;public class Test {public static void main(String[] args) throws InterruptedException {Worker worker1=new Worker("第一个任务", (int)(Math.random()*1000+2000));Worker worker2=new Worker("第二个任务", (int)(Math.random()*1000+2000));Worker worker3=new Worker("第三个任务", (int)(Math.random()*1000+2000));Thread thread1 =new Thread(worker1);Thread thread2 =new Thread(worker2);Thread thread3 =new Thread(worker3);thread1.start();thread2.start();thread1.join();thread2.join();System.out.println("wait thread1 and thread2 complete :");thread3.start();thread3.join();System.out.println("three threads have complete!");}}

package org.pbccrc.org.pbccrc.thread;public class Worker implements Runnable {private String name;private int time;public Worker(String name, int time) {super();this.name = name;this.time = time;}@Overridepublic void run() {System.out.println("task :"+name+":is running!");try {Thread.sleep(time);} catch (InterruptedException e) {e.printStackTrace();}System.out.println("task :"+name+":complete!");}}

task :第一个任务:is running!
task :第二个任务:is running!
task :第二个任务:complete!
task :第一个任务:complete!
wait thread1 and thread2 complete :
task :第三个任务:is running!
task :第三个任务:complete!
three threads have complete!

2、Countdownlatch
采用countDownlatch控制：

package org.pbccrc.org.pbccrc.thread;import java.util.concurrent.CountDownLatch;public class Test {public static void main(String[] args) throws InterruptedException {CountDownLatch latch=new CountDownLatch(2);Worker worker1=new Worker("第一个任务", (int)(Math.random()*1000+2000),latch);Worker worker2=new Worker("第二个任务", (int)(Math.random()*1000+2000),latch);Worker worker3=new Worker("第三个任务", (int)(Math.random()*1000+2000),latch);Thread thread1 =new Thread(worker1);Thread thread2 =new Thread(worker2);Thread thread3 =new Thread(worker3);thread1.start();thread2.start();latch.await();System.out.println("wait thread1 and thread2 complete :");thread3.start();thread3.join();System.out.println("three threads have complete!");}}

package org.pbccrc.org.pbccrc.thread;import java.util.concurrent.CountDownLatch;public class Worker implements Runnable {private String name;private int time;private CountDownLatch latch;public Worker(String name, int time,CountDownLatch latch) {super();this.name = name;this.time = time;this.latch = latch;}@Overridepublic void run() {System.out.println("task :"+name+":is running!");try {Thread.sleep(time);} catch (InterruptedException e) {e.printStackTrace();}System.out.println("task :"+name+":complete!");latch.countDown();    }}

task :第二个任务:is running!
task :第一个任务:is running!
task :第二个任务:complete!
task :第一个任务:complete!
wait thread1 and thread2 complete :
task :第三个任务:is running!
task :第三个任务:complete!
three threads have complete!

我们发现好像join与countdownlatch没有区别：看下面的例子吧：

3、分阶段控制使用countdownlatch

package org.pbccrc.org.pbccrc.thread;import java.util.concurrent.CountDownLatch;public class Worker implements Runnable {private String name;private int time;private CountDownLatch latch;public Worker(String name, int time,CountDownLatch latch) {super();this.name = name;this.time = time;this.latch = latch;}@Overridepublic void run() {System.out.println("task :"+name+":is running for first process!");try {Thread.sleep(time);} catch (InterruptedException e) {e.printStackTrace();}latch.countDown();   try {System.out.println("task :"+name+":is begin for second process!");Thread.sleep(time);System.out.println("task :"+name+":is complete for second process!");} catch (InterruptedException e) {e.printStackTrace();}System.out.println("task :"+name+":complete!");}}

task :第一个任务:is running for first process!
task :第二个任务:is running for first process!
task :第一个任务:is begin for second process!
task :第二个任务:is begin for second process!
wait thread1 and thread2 complete :
task :第三个任务:is running for first process!
task :第一个任务:is complete for second process!
task :第一个任务:complete!
task :第二个任务:is complete for second process!
task :第二个任务:complete!
task :第三个任务:is begin for second process!
task :第三个任务:is complete for second process!
task :第三个任务:complete!
three threads have complete!

区别在：线程执行过程中我们可以使用countdownlatch的方法countDown；countdownlatch是减数器，当数量为0时会唤醒其他的线程执行；

4、CyclicBarrier

public class Test {public static void main(String[] args) throws InterruptedException, BrokenBarrierException {CyclicBarrier barrier=new CyclicBarrier(3);Worker worker1=new Worker("第一个任务", (int)(Math.random()*1000+2000),barrier);Worker worker2=new Worker("第二个任务", (int)(Math.random()*1000+2000),barrier);Worker worker3=new Worker("第三个任务", (int)(Math.random()*1000+2000),barrier);Thread thread1 =new Thread(worker1);Thread thread2 =new Thread(worker2);Thread thread3 =new Thread(worker3);thread1.start();thread2.start();thread3.start();}}

public class Worker implements Runnable {private String name;private int time;private CyclicBarrier  barrier;public Worker(String name, int time,CyclicBarrier barrier) {super();this.name = name;this.time = time;this.barrier = barrier;}@Overridepublic void run() {try {Thread.sleep(time);System.out.println("task :"+name+":has already!");barrier.await();System.out.println("task :"+name+":run !");Thread.sleep(time);} catch (Exception e) {e.printStackTrace();}System.out.println("task :"+name+":complete!");}}

task :第二个任务:has already!
task :第一个任务:has already!
task :第三个任务:has already!
task :第二个任务:run !
task :第三个任务:run !
task :第一个任务:run !
task :第二个任务:complete!
task :第一个任务:complete!
task :第三个任务:complete!

5、区别：CyclicBarrier和CountDownLatch

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