并发

final int total = 3;
ExecutorService executors = Executors.newScheduledThreadPool(total);
final CountDownLatch c = CountDownLatch(total);
//CountDownLatch 是一个同步工具，用来协调多个线程之间的同步 ，或者线程之间的通信
//用法：某一个线程开始运行前等待n个线程执行完毕。每当一个任务线程执行完毕，就将计数器减1，当计数器的值变为0时，在CountDownLatch的await（）的线程就会被唤醒

final AtomicInteger ai = new AtomicInteger(0);
for(int i=0;i<total;i++){
    executors.execute(new Runnable(){
       @Override
        public void run(){
            Long currentTime = System.currentTimeMillis();
            //do something
            Long spendTime = System.currentTimeMills() - currentTime;
            log.info(new Date()+":"+ai.incrementAndGet()+" threads have done!");
            c.countDown();
        }
    });
}
try{
    c.await();
    log.info("............")
    executors.shutdown();
}catch(InterruptedException e){
      log.info(e)
}