hadoop里面的代码片段

高峰之巅

注释的翻译如下：先interrupt所有的线程，在join它们，如果interrupted，就返回false，表明某些线程还在running
/**
   * Try to interrupt all of the given threads, and join on them.
   * If interrupted, returns false, indicating some threads may
   * still be running.
   */
  private boolean interruptAndJoinThreads(List<Thread> threads) {
    // interrupt and wait for all ongoing create threads
    for(Thread t : threads) {
      t.interrupt();
    }
    for(Thread t : threads) {
      try {
        t.join();
      } catch (InterruptedException e) {
        DataNode.LOG.warn("interruptOngoingCreates: t=" + t, e);
        return false;
      }
    }
    return true;
  }
看一看thread的interrupt函数，从注释上看，如果interrupt还没结束就返回join，就会抛出InterruptedException
    /**
     * Interrupts this thread.
     *
     * <p> Unless the current thread is interrupting itself, which is
     * always permitted, the {@link #checkAccess() checkAccess} method
     * of this thread is invoked, which may cause a {@link
     * SecurityException} to be thrown.
     *
     * <p> If this thread is blocked in an invocation of the {@link
     * Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
     * Object#wait(long, int) wait(long, int)} methods of the {@link Object}
     * class, or of the {@link #join()}, {@link #join(long)}, {@link
     * #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
     * methods of this class, then its interrupt status will be cleared and it
     * will receive an {@link InterruptedException}.
     *
     * <p> If this thread is blocked in an I/O operation upon an {@link
     * java.nio.channels.InterruptibleChannel </code>interruptible
     * channel<code>} then the channel will be closed, the thread's interrupt
     * status will be set, and the thread will receive a {@link
     * java.nio.channels.ClosedByInterruptException}.
     *
     * <p> If this thread is blocked in a {@link java.nio.channels.Selector}
     * then the thread's interrupt status will be set and it will return
     * immediately from the selection operation, possibly with a non-zero
     * value, just as if the selector's {@link
     * java.nio.channels.Selector#wakeup wakeup} method were invoked.
     *
     * <p> If none of the previous conditions hold then this thread's interrupt
     * status will be set. </p>
     *
     * <p> Interrupting a thread that is not alive need not have any effect.
     *
     * @throws  SecurityException
     *          if the current thread cannot modify this thread
     *
     * @revised 6.0
     * @spec JSR-51
     */
    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();
return;
    }
}
interrupt0();
    }