CountDownLatch
作用:是一组线程等待其他的线程完成工作以后在执行,加强版join
await 用来等待,countDown 负责计数器的减一
public class UseCountDownLatch {
static CountDownLatch latch = new CountDownLatch(6);
/**
* 初始化线程(只有一步,有4个)
*/
private static class InitThread implements Runnable{
@Override
public void run() {
System.out.println("Thread_" + Thread.currentThread().getId() + " ready init work......");
//初始化线程完成工作了,countDown方法只扣减一次;
latch.countDown();
for(int i =0;i<2;i++) {
System.out.println("Thread_"+Thread.currentThread().getId() +" ........continue do its work");
}
}
}
//业务线程
private static class BusiThread implements Runnable{
@Override
public void run() {
try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
for(int i =0;i<3;i++) {
System.out.println("BusiThread_"+Thread.currentThread().getId()
+" do business-----");
}
}
}
public static void main(String[] args) throws InterruptedException {
new Thread(new BusiThread()).start();
for(int i=0;i<=3;i++){
Thread thread = new Thread(new InitThread());
thread.start();
}
latch.await();
System.out.println("Main done its work........");
}
}
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CyclicBarrier
让一组线程达到某个屏障,被阻塞,一直到组内最后一个线程达到屏障时,屏障开放,所有被阻塞的线程会继续运行
CyclicBarrier(int parties) CyclicBarrier(int parties, Runnable barrierAction),屏障开放,barrierAction 定义的任务会执行
public class UseCyclicBarrier {
private static CyclicBarrier barrier = new CyclicBarrier(5,new CollectThread());
/**
* 存放子线程工作结果的容器
*/
private static ConcurrentHashMap<String,Long> resultMap = new ConcurrentHashMap<>();
public static void main(String[] args) {
for(int i=0;i<=4;i++){
Thread thread = new Thread(new SubThread());
thread.start();
}
}
/**
* 负责屏障开放以后的工作
*/
private static class CollectThread implements Runnable{
@Override
public void run() {
StringBuilder result = new StringBuilder();
for(Map.Entry<String,Long> workResult:resultMap.entrySet()){
result.append("[").append(workResult.getValue()).append("]");
}
System.out.println(" the result = "+ result);
System.out.println("do other business........");
}
}
/**
* 工作线程
*/
private static class SubThread implements Runnable{
@Override
public void run() {
long id = Thread.currentThread().getId();
resultMap.put(Thread.currentThread().getId() + "", id);
//随机决定工作线程的是否睡眠
Random r = new Random();
try {
if(r.nextBoolean()) {
Thread.sleep(2000+id);
System.out.println("Thread_"+id+" ....do something ");
}
System.out.println(id+"....is await");
barrier.await();
Thread.sleep(1000+id);
System.out.println("Thread_"+id+" ....do its business ");
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
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CountDownLatch和CyclicBarrier辨析
- countdownlatch放行由第三者控制,CyclicBarrier放行由一组线程本身控制
- countdownlatch放行条件》=线程数,CyclicBarrier放行条件=线程数