使用sleep方法暂停一个线程

Pausing Execution with Sleep

使用sleep方法暂停一个线程 

Thread.sleep causes the current thread to suspend execution for a specified period. This is an efficient means of making processor time available to the other threads of an application or other applications that might be running on a computer system. The sleep method can also be used for pacing, as shown in the example that follows, and waiting for another thread with duties that are understood to have time requirements, as with the SimpleThreads example in a later section.使用Thread.sleep()方法可以暂停当前线程一段时间。这是一种使处理器时间可以被其他线程或者应用程序使用的有效方式。sleep()方法还可以用于调整线程执行节奏（见下面的例子）和等待其他有执行时间需求的线程（这个例子将在下一节演示）。

Two overloaded versions of sleep are provided: one that specifies the sleep time to the millisecond and one that specifies the sleep time to the nanosecond. However, these sleep times are not guaranteed to be precise, because they are limited by the facilities provided by the underlying OS. Also, the sleep period can be terminated by interrupts, as we'll see in a later section. In any case, you cannot assume that invoking sleep will suspend the thread for precisely the time period specified.在Thread中有两个不同的sleep()方法，一个使用毫秒表示休眠的时间，而另一个使用纳秒。由于操作系统的限制休眠时间并不能保证十分精确。休眠周期可以被interrupts所中断，我们将在后面看到这样的例子。不管在任何情况下，我们都不应该假定调用了sleep()方法就可以将一个线程暂停一个十分精确的时间周期。

The SleepMessages example uses sleep to print messages at four-second intervals:

SleepMessages程序为我们展示了使用sleep()方法每四秒打印一个信息的例子 

public class SleepMessages {
    public static void main(String args[])
        throws InterruptedException {
        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);
            //Print a message
            System.out.println(importantInfo[i]);
        }
    }
}

Notice that main declares that it throws InterruptedException. This is an exception that sleep throws when another thread interrupts the current thread while sleep is active. Since this application has not defined another thread to cause the interrupt, it doesn't bother to catch InterruptedException.  main()方法声明了它有可能抛出InterruptedException。当其他线程中断当前线程时，sleep()方法就会抛出该异常。由于这个应用程序并没有定义其他的线程，所以并不用关心如何处理该异常。