并发中Interrupt的相关知识

Interrupt

interrupt()是线程类的成员方法，作用是打断线程

与之有关的还有isInterrupted()和interrupted()

interrupt()的作用是分情况的

当线程被join()、sleep()、wait()阻塞的时候

使用此方法，会设置打断标记为false，并且抛出异常InterruptedException

当线程正在运行的时候

使用此方法，会设置打断标记为true，但是不会影响线程继续运行

当线程使用LockSupport.park()挂起

使用此方法，会设置打断标记为true，但是不会抛出异常

Tips：在打断状态下，无法使用LockSupport.park()挂起当前线程

/**
 * 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 InterruptibleChannel}
 * 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();

        // thread may be blocked in an I/O operation
        synchronized (blockerLock) {
            Interruptible b = blocker;
            if (b != null) {
                interrupt0();  // set interrupt status
                b.interrupt(this);
                return;
            }
        }
    }

    // set interrupt status
    interrupt0();
}

isInterrupted

此方法也是线程类的成员方法，作用是返回打断标记

/**
 * Tests whether this thread has been interrupted.  The <i>interrupted
 * status</i> of the thread is unaffected by this method.
 *
 * <p>A thread interruption ignored because a thread was not alive
 * at the time of the interrupt will be reflected by this method
 * returning false.
 *
 * @return  {@code true} if this thread has been interrupted;
 *          {@code false} otherwise.
 * @see     #interrupted()
 * @revised 6.0
 */
public boolean isInterrupted() {
    return isInterrupted(false);
}

interrupted

此方法是Thread的静态方法，作用是重置当前运行线程的打断标记（就是将打断标记置为false），并返回之前的打断标记

/**
     * Tests whether the current thread has been interrupted.  The
     * <i>interrupted status</i> of the thread is cleared by this method.  In
     * other words, if this method were to be called twice in succession, the
     * second call would return false (unless the current thread were
     * interrupted again, after the first call had cleared its interrupted
     * status and before the second call had examined it).
     *
     * <p>A thread interruption ignored because a thread was not alive
     * at the time of the interrupt will be reflected by this method
     * returning false.
     *
     * @return  {@code true} if the current thread has been interrupted;
     *          {@code false} otherwise.
     * @see #isInterrupted()
     * @revised 6.0
     */
public static boolean interrupted() {
    return currentThread().isInterrupted(true);
}