Java多线程 中断机制及实例详解

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.chttp://urrentThread())

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() {

dCTgEreturn 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

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