The Java™ Tutorials — Concurrency ：The SimpleThreads Example SimpleThreads案例

The Java™ Tutorials — Concurrency ：The SimpleThreads Example SimpleThreads案例

原文地址：https://docs.oracle.com/javase/tutorial/essential/concurrency/simple.html

关键点

理解文中的案例

全文翻译

The following example brings together some of the concepts of this section. SimpleThreads consists of two threads. The first is the main thread that every Java application has. The main thread creates a new thread from the Runnable object, MessageLoop, and
waits for it to finish. If the MessageLoop thread takes too long to finish, the main thread interrupts it.

下面的案例会将本课时的几个概念结合起来。SimpleThreads由两个线程组成。首先是主线程，这个每个Java程序都有。主线程利用Runnable对象创建了一个新线程MessageLoop，并等待直到新线程完成。如果MessageLoop线程占用了太长时间，那么主线程就会中断它。

The MessageLoop thread prints out a series of messages. If interrupted before it has printed all its messages, the MessageLoop thread prints a message and exits.

MessageLoop线程会打印出一些列消息。如果中断在消息打印完之前发生，那此线程就会打出一条信息并退出。

public class SimpleThreads {

// Display a message, preceded by
// the name of the current thread
static void threadMessage(String message) {
String threadName = Thread.currentThread().getName();
System.out.format("%s: %s%n", threadName, message);
}

private static class MessageLoop implements Runnable {
public void run() {
String importantInfo[] = { "Mares eat oats", "Does eat oats",
"Little lambs eat ivy", "A kid will eat ivy too" };
try {
for (int i = 0; i < importantInfo.length; i++) {
// Pause for 4 seconds
Thread.sleep(4000);
// Print a message
threadMessage(importantInfo[i]);
}
} catch (InterruptedException e) {
threadMessage("I wasn't done!");
}
}
}

public static void main(String args[]) throws InterruptedException {

// Delay, in milliseconds before
// we interrupt MessageLoop
// thread (default one hour).
long patience = 1000 * 60 * 60;

// If command line argument
// present, gives patience
// in seconds.
if (args.length > 0) {
try {
patience = Long.parseLong(args[0]) * 1000;
} catch (NumberFormatException e) {
System.err.println("Argument must be an integer.");
System.exit(1);
}
}

threadMessage("Starting MessageLoop thread");
long startTime = System.currentTimeMillis();
Thread t = new Thread(new MessageLoop());
t.start();

threadMessage("Waiting for MessageLoop thread to finish");
// loop until MessageLoop
// thread exits
while (t.isAlive()) {
threadMessage("Still waiting...");
// Wait maximum of 1 second
// for MessageLoop thread
// to finish.
t.join(1000);
if (((System.currentTimeMillis() - startTime) > patience)
&& t.isAlive()) {
threadMessage("Tired of waiting!");
t.interrupt();
// Shouldn't be long now
// -- wait indefinitely
t.join();
}
}
threadMessage("Finally!");
}
}