Interrupt, interrupted, isinterrupted differences

interrupt、interrupted 、isInterrupted difference

One 、interrupt

A thread should not be forced to interrupt or stop by other threads , It should be stopped by the thread itself . therefore ,Thread.stop, Thread.suspend, Thread.resume It's been abandoned .

and Thread.interrupt() In fact, it's not to interrupt threads , It is The notification thread should be broken , Whether to interrupt or continue to run , It should be handled by the notified thread itself .

say concretely , When a thread calls interrupt() When the method is used ：

① If the thread is blocked （ For example, in the sleep, wait, join Equal state ）, Then the thread will immediately exit the blocking state , And throw a InterruptedException abnormal , That's it , Interrupt flag remains false.

② If the thread is active , The thread's interrupt flag will be set to true, That's it , Does not throw an exception . The thread with interrupt flag will continue to run normally , Unaffected .

③ If a thread is in park state （ Sleep ） when （ call Unsafe.park() perhaps LockSupport.park()), call interrupt() Method sets the interrupt flag to true And immediately return , however Don't throw InterruptedException abnormal .

in summary ,interrupt() Methods don't really interrupt threads , It needs to be handled by the called thread itself .

in other words , If a thread needs to be interrupted , So you can do this ：

① In the normal operation of the task , Check the interrupt flag bit of this thread frequently , If the interrupt flag is set to true Just stop the thread .

② Threads that are blocked should handle InterruptedException abnormal , for example catch Stop the thread after the exception .

Two 、interrupted

Source code is as follows ：

public static boolean interrupted() {
    
    // Called the of the current thread isInterrupted Method , Parameter passing true
    return currentThread().isInterrupted(true);
}

3、 ... and 、isInterrupted

call isInterrupted() The source code of the method is as follows ：

public boolean isInterrupted() {
    
    // Subsequent call isInterrupted Method , It's just parameter passing false
    return isInterrupted(false);
}

interrupted and isInterrupted There are two main differences between the two methods ：

1. interrupted Is for the current thread ,isInterrupted Is the thread corresponding to the thread object that calls the method .（ The thread corresponding to the thread object is not necessarily the currently running thread . For example, it can be in A Call in thread B Of Thread objects isInterrupted Method ）
2. Both methods end up calling the same method , Only one parameter is true, One is false.

Finally called isInterrupted() The source code of the method is as follows ：

// It's a local approach 
private native boolean isInterrupted(boolean ClearInterrupted);

From the parameter name, you can know that the function of the parameter is Whether to clear the status bit .

If this parameter is zero true, Indicates the status flag of the thread to be cleared , That is to say, set it as false; If the parameter is false, Directly return the status bit of the thread , The state is not modified .

isInterrupted() and interrupt() It's an instance method , You must call... Through an object instance ;interrupted() It's a static method , Methods at the class level .