安全地终止线程
在中断线程节中提到的中断状态是线程的一个标识位,而中断操作是一种简便的线程间交互方式,而这种交互方式最适合用来取消或停止任务。除了中断以外,还可以利用一个boolean变量来控制是否需要停止任务并终止该线程。在代码清单1所示的例子中,创建了一个线程CountThread,它不断地进行变量累加,而主线程尝试对其进行中断操作和停止操作。
清单1
package com.ise.api.thread;
import java.util.concurrent.TimeUnit;
public class Shutdown {
public static void main(String[] args) throws Exception {
Runner one = new Runner();
Thread countThread = new Thread(one, "CountThread");
countThread.start();
// 睡眠1秒,main线程对CountThread进行中断,使CountThread能够感知中断而结束
TimeUnit.SECONDS.sleep(1);
countThread.interrupt();
Runner two = new Runner();
countThread = new Thread(two, "CountThread");
countThread.start();
// 睡眠1秒,main线程对Runner two进行取消,使CountThread能够感知on为false而结束
TimeUnit.SECONDS.sleep(1);
two.cancel();
}
private static class Runner implements Runnable {
private long i;
private volatile boolean on = true;
@Override
public void run() {
while (on && !Thread.currentThread().isInterrupted()) {
i++;
}
System.out.println("Count i = " + i);
}
public void cancel() {
on = false;
}
}
}
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