如何创建一个在Java中接受回调函数的方法？

Question

I created a distributed lock class that I designed to be used like this:

myLock.lock();
doSomething();
myLock.unlock();

In my current implementation, lock() blocks until the lock is acquired. But I am running into some deadlock issues with this implementation. So I'd like to rewrite it to be asynchronous, but I have no idea how to do that in java.

Something like this would work I think:

myLock.lock(myCallbackFunction);

private void myCallbackFunction(boolean result){
    if(result){
        doSomething();
        mylock.Unlock();
    }
}

Is there a way to do this in java?

EDIT (More detail): The reasons why the synchronous implementation is deadlocking are complicated and not relevant. The distributed lock is acquiring mutual exclusion of a resource across a network with multiple systems. Really the only thing I'm looking for is how to write a method that accepts a callback function.

Answer 1

You can't do that in Java yet. What you can do is define a LockCallback interface:

interface LockCallback {
  void run(boolean result, MyLock lock);
}

and have MyLock#lock take a LockCallback as a parameter. Then callers can call it as

myLock.lock(new LockCallback {
  public void run(boolean result, MyLock lock) {
    // ... do whatever needs to be done ...
    lock.unlock();
  });

Lambda syntax in Java 8 should make this a little less ugly looking.

Answer 2

与其编写自己的想法，然后由于无法实现而放弃想法，为什么不使用Semaphore ，它已经存在并且可以正确实现？