在DEMO測試中，我有個需求描述如下：線程A、B、C、D，我需要他們同時開始運行，並記錄這四個線程全部完成所需要的時間。
這個藉助synchronizer可輕鬆完成。這裏我們使用CountDownLatch來實現，該方法的詳細描述參見我的上篇博文：點擊打開鏈接
核心代碼如下：demo請參見github
/**
* @param args
* @throws InterruptedException
*/
private static long timer(Executor e,int concurrency,final Runnable action) throws InterruptedException{
final CountDownLatch ready = new CountDownLatch(concurrency);
final CountDownLatch start = new CountDownLatch(1);
final CountDownLatch end = new CountDownLatch(concurrency);
//將線程同時啓動並處於wait狀態，知道start.await因爲countDown=0被啓動
for(int i=0;i<concurrency;i++){
e.execute(new Runnable(){
@Override
public void run() {
// TODO Auto-generated method stub
ready.countDown();
try {
start.await();
System.out.print(Thread.currentThread().getId()+"ready\n");
action.run();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
Thread.currentThread().interrupt();
}finally{
System.out.print(Thread.currentThread().getId()+"end\n");
end.countDown();
}
}
});
}
ready.await();
start.countDown();
long startTime = System.nanoTime();
end.await();
return System.nanoTime()-startTime;調用方法：
public static void main(String[] args) {
// TODO Auto-generated method stub
i = new AtomicInteger();
ExecutorService e = Executors.newFixedThreadPool(5);
Runnable action = new Runnable(){
@Override
public void run() {
// TODO Auto-generated method stub
try {
//System.out.print(i.get()+"\n");
TimeUnit.SECONDS.sleep(i.getAndAdd(5));
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
};
try {
long time = timer(e, 4, action);
System.out.println(time);
} catch (InterruptedException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
e.shutdown();
}