java 线程解读(C++)

1. 线程状态: NEW, RUNNABLE, BLOCKED,WAITING, TIMED_WAITING, TERMINATED
2. 线程方法:
   2.1 启动线程-start

public synchronized void start() {
      /**
       * This method is not invoked for the main method thread or "system"
       * group threads created/set up by the VM. Any new functionality added
       * to this method in the future may have to also be added to the VM.
       *
       * A zero status value corresponds to state "NEW".
       */
      if (threadStatus != 0)
          throw new IllegalThreadStateException();

      /* Notify the group that this thread is about to be started
       * so that it can be added to the group's list of threads
       * and the group's unstarted count can be decremented. */
      group.add(this);

      boolean started = false;
      try {
          start0();
          started = true;
      } finally {
          try {
              if (!started) {
                  group.threadStartFailed(this);
              }
          } catch (Throwable ignore) {
              /* do nothing. If start0 threw a Throwable then
                it will be passed up the call stack */
          }
      }
  }
private native void start0();

2.2 中断线程方法-interrupt

  void os::interrupt(Thread* thread) {
  assert(Thread::current() == thread || Threads_lock->owned_by_self(),
    "possibility of dangling Thread pointer");

  OSThread* osthread = thread->osthread();

  if (!osthread->interrupted()) {
    osthread->set_interrupted(true);
    // More than one thread can get here with the same value of osthread,
    // resulting in multiple notifications.  We do, however, want the store
    // to interrupted() to be visible to other threads before we execute unpark().
    OrderAccess::fence();
    ParkEvent * const slp = thread->_SleepEvent ;
    if (slp != NULL) slp->unpark() ;
  }

  // For JSR166. Unpark even if interrupt status already was set
  if (thread->is_Java_thread())
    ((JavaThread*)thread)->parker()->unpark();

  ParkEvent * ev = thread->_ParkEvent ;
  if (ev != NULL) ev->unpark() ;

}
中断线程并不是停止线程，而是变更线程的中断状态(_interrupted), 停止线程需要相应的业务逻辑!!!
C++{
volatile jint _interrupted;     // Thread.isInterrupted state
}

2.3 查看中断状态方法-isInterrupted

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

bool os::is_interrupted(Thread* thread, bool clear_interrupted) {
  assert(Thread::current() == thread || Threads_lock->owned_by_self(),
    "possibility of dangling Thread pointer");

  OSThread* osthread = thread->osthread();

  bool interrupted = osthread->interrupted();

  if (interrupted && clear_interrupted) {
    osthread->set_interrupted(false);
    // consider thread->_SleepEvent->reset() ... optional optimization
  }

  return interrupted;
}

2.4 查看中断状态并清除中断标志-interrupted

  public static boolean interrupted() {
      return currentThread().isInterrupted(true);
  }
 返回当前线程的中断状态，并将中断标识设置为0；

  volatile bool interrupted() const                 { return _interrupted != 0; }
  void set_interrupted(bool z)                      { _interrupted = z ? 1 : 0; }