线程

synchronized和ReentrantLock之多线程同步详解

https://www.jianshu.com/p/96c89e6e7e90

notify（），notifyAll（）锁池，等待池

https://blog.youkuaiyun.com/djzhao/article/details/79410229

让线程阻塞的几种方法join()方法,Executor的invokeAll()方法,future.get()方法

ExecutorService exec= Executors.newFixedThreadPool(5);
try {
    List<Future<String>> futures = exec.invokeAll(new ArrayList<Callable<String>>());
} catch (InterruptedException e) {
    e.printStackTrace();
}