Java Equivalent of .NET's ManualResetEvent and WaitHandle

Question

I would like to know if Java provides an equivalent of .NET's classes of ManualResetEvent and WaitHandle, as I would like to write code that blocks for a given timeout unless an event is triggered. The .NET classes of WaitHandle and ManualResetEvent provide a nice, hassle-free interface for that which is also thread-safe as far as I know, so what does Java has to offer?

Accepted Answer

Have you considered using `wait`/`notify` (the equivalent of `Monitor.Wait` and `Monitor.Pulse`) instead?

You'll want a little bit of checking to see whether you actually need to wait (to avoid race conditions) but it should work.

Otherwise, something like `CountDownLatch` may well do what you want.

EDIT: I've only just noticed that `CountDownLatch` is basically "single use" - you can't reset the count later, as far as I can see. You may want `Semaphore` instead. Use `tryAcquire` like this to wait with a timeout:

```
if (semaphore.tryAquire(5, TimeUnit.SECONDS)) {
   ...
   // Permit was granted before timeout
} else {
   // We timed out while waiting
}
```

Note that this is unlike `ManualResetEvent` in that each successful call to `tryAcquire` will reduce the number of permits - so eventually they'll run out again. You can't make it permanently "set" like you could with `ManualResetEvent`. (That would work with `CountdownLatch`, but then you couldn't "reset" it :)

Java Equivalent of .NET's ManualResetEvent and WaitHandle

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