Thread() sleep()

照着官方手册：

public class SleepMessages {
    public static void main(String args[])
            throws InterruptedException {   //当sleep过程中有其他线程打断了当前线程，可以抛出这个异常。
        String importantInfo[] = {
                "Mares eat oats",
                "Does eat oats",
                "Little lambs eat ivy",
                "A kid will eat ivy too"
        };

        for (int i = 0;
             i < importantInfo.length;
             i++) {
            //Pause for 4 seconds
            Thread.sleep(4000);  //单位millis 千分之一秒
            //Print a message
            System.out.println(importantInfo[i]);
        }
    }
}

结果：每隔一段时间打印一行，直到四行打印完毕，当前线程由于被sleep（）以后，所以才会断断续续执行。

Mares eat oats
Does eat oats
Little lambs eat ivy
A kid will eat ivy too

来看sleep（）方法：

sleep是一个native方法。native方法怎么实现不在讨论范围之内。

/**
     * Causes the currently executing thread to sleep (temporarily cease
     * execution) for the specified number of milliseconds, subject to
     * the precision and accuracy of system timers and schedulers. The thread
     * does not lose ownership of any monitors.
     *
     * @param  millis
     *         the length of time to sleep in milliseconds
     *
     * @throws  IllegalArgumentException
     *          if the value of {@code millis} is negative
     *
     * @throws  InterruptedException
     *          if any thread has interrupted the current thread. The
     *          <i>interrupted status</i> of the current thread is
     *          cleared when this exception is thrown.
     */
    public static native void sleep(long millis) throws InterruptedException;

Java官方英文手册https://docs.oracle.com/javase/tutorial/essential/concurrency/runthread.html