Java多线程（十二）：中断机制

谁践踏了优雅 2023-08-17 15:16 157阅读 0赞

这里详细分析interrupt(),interrupted(),isInterrupted()三个方法

## interrupt() ##

中断这个线程，设置中断标识位

public void interrupt() { if (this != Thread.currentThread()) checkAccess(); synchronized (blockerLock) { Interruptible b = blocker; if (b != null) { interrupt0(); // Just to set the interrupt flag b.interrupt(this); return; } } interrupt0(); }

我们来找下如何设置中断标识位的  
找到interrupt0()的源码，src/hotspot/share/prims/jvm.cpp

JVM_ENTRY(void, JVM_Interrupt(JNIEnv* env, jobject jthread))
      ...
      if (is_alive) {
        // jthread refers to a live JavaThread.
        Thread::interrupt(receiver);
      }
    JVM_END

调用了Thread::interrupt方法  
src/hotspot/share/runtime/thread.cpp

void Thread::interrupt(Thread* thread) {
      ...
      os::interrupt(thread);
    }

os::interrupt方法，src/hotspot/os/posix/os\_posix.cpp

void os::interrupt(Thread* thread) {
      ...
      OSThread* osthread = thread->osthread();
      if (!osthread->interrupted()) {
        //设置中断标识位
        osthread->set_interrupted(true);
        ...
      }
        ...
    }

## isInterrupted() ##

测试线程是否被中断，线程的中断状态不会改变

public boolean isInterrupted() { return isInterrupted(false); }

查看native isInterrupted(boolean ClearInterrupted)源码，查找方式同上  
src/hotspot/os/posix/os\_posix.cpp

bool os::is_interrupted(Thread* thread, bool clear_interrupted) {
      debug_only(Thread::check_for_dangling_thread_pointer(thread);)
    
      OSThread* osthread = thread->osthread();
      // 查看是否被中断
      bool interrupted = osthread->interrupted();
    
      // 清除标识位后再设置false
      if (interrupted && clear_interrupted) {
        osthread->set_interrupted(false);
      }
    
      return interrupted;
    }

Java传递ClearInterrupted为false，对应C++的clear\_interrupted

## interrupted() ##

测试线程是否被中断，清除中断标识位

public static boolean interrupted() { return currentThread().isInterrupted(true); }

**简单的例子**

public class MyThread45 { public static void main(String[] args) throws Exception { Runnable runnable = new Runnable() { public void run() { while (true) { if (Thread.currentThread().isInterrupted()) { System.out.println("线程被中断了"); return ; } else { System.out.println("线程没有被中断"); } } } }; Thread t = new Thread(runnable); t.start(); Thread.sleep(500); t.interrupt(); System.out.println("线程中断了，程序到这里了"); } }

检查线程是否中断，中断线程，运行结果如下

······
    线程没有被中断
    线程没有被中断
    线程没有被中断
    线程被中断了
    线程中断了，程序到这里了

转载于:https://www.cnblogs.com/Java-Starter/p/11470748.html