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
publicvoidinterrupt(){ if(this!=Thread.currentThread()) checkAccess(); synchronized(blockerLock){ Interruptibleb=blocker; if(b!=null){ interrupt0();//Justtosettheinterruptflag 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,jobjectjthread)) ... if(is_alive){ //jthreadreferstoaliveJavaThread. Thread::interrupt(receiver); } JVM_END
调用了Thread::interrupt方法
src/hotspot/share/runtime/thread.cpp
voidThread::interrupt(Thread*thread){ ... os::interrupt(thread); }
os::interrupt方法,src/hotspot/os/posix/os_posix.cpp
voidos::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
publicbooleanisInterrupted(){ returnisInterrupted(false); }
查看nativeisInterrupted(booleanClearInterrupted)源码,查找方式同上
src/hotspot/os/posix/os_posix.cpp
boolos::is_interrupted(Thread*thread,boolclear_interrupted){ debug_only(Thread::check_for_dangling_thread_pointer(thread);) OSThread*osthread=thread->osthread(); //查看是否被中断 boolinterrupted=osthread->interrupted(); //清除标识位后再设置false if(interrupted&&clear_interrupted){ osthread->set_interrupted(false); } returninterrupted; }
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
publicstaticbooleaninterrupted(){ returncurrentThread().isInterrupted(true); }
简单的例子
publicclassMyThread45{ publicstaticvoidmain(String[]args)throwsException { Runnablerunnable=newRunnable() { publicvoidrun() { 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"); } } } }; Threadt=newThread(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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