异步任务批量执行

ExecutorService executorService=Executors.newFixedThreadPool(10);
        CompletionService completionService=new ExecutorCompletionService(executorService);
        for (int i=0;i<10;i++){
            int finalI = i;
            completionService.submit(new Callable() {
                @Override
                public Object call() throws Exception {
                    System.out.println(finalI);
                    return null;
                }
            });
        }

结果:
0
3
1
4
5
2
6
7
8
9

为什么要批量执行? 看下面的代码说明:

Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("thread1");
            }
        });
        thread1.start();
        Thread thread2 = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("thread2");
            }
        });
        thread2.start();

执行结果:
thread1
thread2

看到上面的这个结果, 如果是高并发的情况下其实已经失去了意义, 其结果都是从上到下执行