Java多线程 中断机制及实例详解

正文

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

以上就是本文的全部内容，希望对大家的学习有所帮助

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