线程全部结束与集合点

final int size = 50;

final CountDownLatch countDown = new CountDownLatch(size);//执行计数
final CyclicBarrier barrier = new CyclicBarrier(size);    //集合点
ExecutorService exec = Executors.newFixedThreadPool(size);   

long start = System.currentTimeMillis();

for(int index=1; index <= size; index++ ){ 

    final int indexCopy = index;   
    Runnable run = new Runnable() {   
        public void run() {   
            try {   
                    System.out.println(indexCopy+"号就绪!");   
                    barrier.await();//等待所有线程集合   
                    System.out.println(indexCopy+"号开始执行!");   
            } catch (Exception e) {   
                    e.printStackTrace();   
            }   
            finally{   
                countDown.countDown();//释放   
            }   
        }   
    };   
    exec.execute(run);      
}     
countDown.await();//等待线程完成   
exec.shutdown();    
//统计时间   

System.out.println("结束时间："+sdf.format(endDate));