Java thread.isInterrupted() 返回值不确定结果分析解决
目录
- 一、代码
- 二、分析结果
- 三、解决方案
一、代码
先上代码(以下这段代码会有多种执行结果)
@Test public void test_interrupted_thread() throws Exception { InterruptThread interruptThread = new InterruptThread(); interruptThread.start(); interruptThread.interrupt(); System.out.println("interruptThread.isInterrupted():" + interruptThread.isInterrupted()); } public class InterruptThread extends Thread { @Override public void run() { for (int i=0; i< 3; i++) { System.out.println("i=" + (i + 1)); } System.out.println("【InterruptThread】结束"); } }
执行结果1:
i=1
i=2
i=3
【Thread-0】【InterruptThread】结束
【main】interruptThread.isInterrupted():false
执行结果2:
【main】interruptThread.isInterrupted():true
i=1
i=2
i=3
【Thread-0】【InterruptThread】结束
执行结果3:
i=1
i=2
i=3
【Thread-0】【InterruptThread】结束
【main】interruptThread.isInterrupted():true
二、分析结果
执行结果1:
Main线程调用了interruptThread.start();,interruptThread线程启动,执行了interruptThread线程内容,同时Main线程调用了interruptThread.interrupt();,设定了interruptThread线程中断标记为true,最后InterruptThread结束,清除中断标记,Main线程调用interruptThread.isInterrupted() 获取interruptThread线程中断标记为false。
执行结果2:
Main线程调用了interruptThread.start();,interruptThread线程启动,但是由于CPU随机调度,在执行了interruptThread线程内容前,先执行Main线程调用interruptThread.interrupt();,设定了interruptThread线程中断标记为true,且先调用interruptThread.isInterrupted()获取interruptThread线程中断标记为true并输出,最后在执行interruptThread线程内容。
执行结果3:
Main线程调用了interruptThread.start();,interruptThread线程启动,执行了interruptThread线程内容,同时Main线程调用了interruptThread.interrupt();,设定了interruptThread线程中断标记为true,最后InterruptThread结束,但是Main线程调用interruptThread.isInterrupted() 获取interruptThread线程中断标记为true。(与执行结果1执行顺序一致,但是最终结果不一致)
原因分析:
Main线程调用interruptThread.interrupt()后立即调用interruptThread.isInterrupted(),虽然interruptThread执行结束,但有可能在interruptThread线程还未完成清除打断标记就Main线程就查看打断标记,此时仍然为true。
三、解决方案
如果Main线程要得到稳定的false,即重置打断标记后的结果,有如下方案:
(1)需要Main线程在调用interruptThread.interrupt();,对Main线程sleep一会,给点时间,再通过调用interruptThread.isInterrupted()获取interruptThread线程的中断状态。
@Test public void test_interrupted_thread() throws Exception { InterruptThread interruptThread = new InterruptThread(); interruptThread.start(); interruptThread.interrupt(); Thread.sleep(100); System.out.println("【" + Thread.currentThread().getName() + "】" + "interruptThread.isInterrupted():" + interruptThread.isInterrupted()); }
(2)也可以通过Main线程调用interruptThread.join(),让Main线程等到interruptThread执行直到中止后再调用interruptThread.isInterrupted()获取interruptThread线程的中断状态。
@Test public void test_interrupted_thread() throws Exception { InterruptThread interruptThread = new InterruptThread(); interruptThread.start(); interruptThread.interrupt(); interruptThread.join(); System.out.println("【" + Thread.currentThread().getName() + "】" + "interruptThread.isInterrupted():" + interruptThread.isInterrupted()); }
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