Thread.join()
CountDownLatch.await()
CyclicBarrier.await()
三者都是用来控制程序的“流动” 可以让程序“堵塞”在某几个点 以利用经由多线程操作后的某些最终结果
eg1:
1 public class joinTest {
2
3 private static Thread[] ts = new Thread[10];
4 private static AtomicInteger ai = new AtomicInteger(0);
5
6 public joinTest() {
7 for (int i = 0; i < 10; i++) {
8 ts[i] = new Thread() {
9 @Override
10 public void run() {
11 try {
12 Thread.sleep(100);
13 }catch (Exception e){
14
15 }
16 ai.incrementAndGet();
17 }
18 };
19 }
20 }
21
22
23
24
25 public static void main(String[] args) throws Exception {
26
27 new joinTest();
28
29 for (int i = 0; i < 10; i++) {
30 ts[i].start();
31 }
32
33 for (int i = 0; i < 10; i++) {
34 ts[i].join();
35 }
36
37 System.out.println(ai);
38
39 }
40
41 }
此时输出为10
注意在run方法中的sleep操作，此时必须写到try/catch代码块内，因为异常不能跨线程传播 所以不能写在方法尾部throws！
eg2:
public class controlThread {
private static final int ThreadCount = 500;
private static AtomicInteger result = new AtomicInteger(0);
private static CountDownLatch endCount = new CountDownLatch(ThreadCount);
static void helper(){
for(int i=0;i<500;i++){
new Thread() {
@Override
public void run() {
result.incrementAndGet();
endCount.countDown();
}
}.start();
}
}
public static void main(String[] args) throws Exception{
new Thread(){
@Override
public void run(){
helper();
}
}.start();
endCount.await();
//Thread.sleep(10);
print(result);
}
}
此时result结果为500
如果注释掉await() 加上sleep 则数值随机
全都注释掉一般情况为0
eg3:
public class cyclicBarrierTest {
private static CyclicBarrier cyclic = new CyclicBarrier(5,new BarrierRun());
private static boolean flag = false;
static class BarrierRun implements Runnable{
@Override
public void run(){
if(!flag)
print("we five are ready!");
else
print("we five are ready again!");
}
}
public static void main(String[] args) throws Exception {
for (int i = 0; i < 5; i++) {
new Thread() {
@Override
public void run() {
try {
print(Thread.currentThread()+"'s worker has comed");
cyclic.await();
flag = true ;
print(Thread.currentThread()+"wait you five so long!");
cyclic.await();
} catch (Exception e) {
e.printStackTrace();
}
}
}.start();
}
}
}
只有当指定数目的线程进入到cyclic.await()方法处，才会让各个线程继续执行。 而且该方法可以复用。
这里如果某一个线程被中断，其他程序将不会愚蠢的等待 人到齐了 再执行接下来的任务 此时程序报错
