适用的情况
当想要终止正在运行的线程, 如果突然被紧急终止了, 那么这时候的实例的状态可能就会出现错误.
实现的方式
可能会被中断的线程, 轮询线程的状态或者捕获InterruptException进行处理, 利用finally{}确保线程关闭的时候维护相关状态的安全.
相关的模式
- 当想在执行终止处理前禁止其他处理, 可以使用Balking模式.
代码示例:
这是一个负责慢慢累加的CountUpThread"线程"类, 他会在接收到终止通知的时候, 打印最后counter的大小.
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package com.graphic.twoPhaseTermination;
/**
* @author youngxinler 19-6-4 下午5:36
* @version 0.1
* <p>
* 这里有一点不懂, 如果去掉shutdownRequested变量, 那么由无论是内部还是外部去调用isInterrupted()方法, 判断线程是否中断的话, isInterrupted()方法的返回结果一直是false.
* <p>
* 加上shutdownRequested方法的话, 使用isShutdownRequested()来判断"逻辑上的线程中断"是好使的, 但是为什么isInterrupted()就不行呢? 这难道是个"鬼才方法"? 调用isInterrupted()会自动结束线程的中断状态?
**/
public class CountUpThread extends Thread {
private long counter = 0;
private volatile boolean shutdownRequested = false;
public void shutdown() {
shutdownRequested = true;
interrupt();
}
public boolean isShutdownRequested() {
return shutdownRequested;
}
@Override
public void run() {
try {
while (true) {
doWork();
}
} catch (InterruptedException e) {
System.out.println("i get the interruptedException");
System.out.println("self check counterThread isInterrupt " + isInterrupted());
interrupt();
} finally {
doShutdown();
}
}
private void doWork() throws InterruptedException {
counter++;
System.out.println("doWork: counter = " + counter);
Thread.sleep(500);
}
private void doShutdown() {
System.out.println("doShutdown: counter = " + counter);
}
}
package com.graphic.twoPhaseTermination;
/**
* @author youngxinler 19-6-4 下午5:47
* @version 0.1
**/
public class Main {
public static void main(String[] args) {
System.out.println("main : start");
try {
CountUpThread countUpThread = new CountUpThread();
countUpThread.start();
Thread.sleep(10000);
System.out.println("main : shutdownRequest");
countUpThread.shutdown();
System.out.println("main : join");
countUpThread.join();
System.out.println("main check counterThread isShutdownRequested " + countUpThread.isShutdownRequested());
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("main : end");
}
}
