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java listening file system double click

I have this example to listening events from fileSystem (http://java.dzone.com/news/how-watch-file-system-changes) but the events are only create, delete or modify.
I want to listen a simple double click event from my fileSystem.
Does anyone know how to do it? I can't do it by swing.
Thanks!

Java, out of the box, is not capable of watching for "a simple double click event from my fileSystem".
The link you mention is about java code that can watch for other types of events, such as create, delete and modify within the file system, but double clicks are "user interface" events, which are not covered by java code as such.
However, you have rightly mentioned Swing.
If you wrote a programme, using Swing, that was specifically designed to make changes to the file system, then yes, your programme could be written to listen for clicks on a button on a swing layout, and your code could then decide what to do with that click event.

There is no such thing as a "double click event" in terms of the subject you're talking about.
The WatchService in Java is an interface with the implementation being platform specific (including being completely optional, depending on the platform).
The way the default implementation works on some platforms (specifically, windows / *nix) is by periodically polling the filesystem metadata for the directory you specified. If the default implementation is not monitoring access time (atime) or it's not available on the platform (or is turned off), then ... no, you can't get events for file access.
Testing this on OSX, it does not. I would have to test it on Windows and *nix to see what the results were there. I don't know that any of the default implementations do as atime isn't really reliable as it can be turned off on many file systems that support it to improve performance.
If you wanted to use the WatchService interface for this and the platform(s) your code would run on support it, you could implement your own that looked at access time and fired an event.
This StackOverflow Question demonstrates how to check atime on a file, but again remember it's not really reliable (read the comments on the caveats).

Check for keystroke

Im making an application that should see if your online or away.
So i need to somehow see when the user hit a key on the keyboard last time.
The application is running in the background and you can only access it from the trey.
Is this possible and if it is how would i check.
Best regards

I believe that what you're looking for can be done via a global keyboard hook, but that doesn't have direct support in the JVM. From Googling, it would appear that your only options are to write a C++ shim which you can use via JNI, or go via libffi with JRuby.

From what I've read here it is not possible to add KeyListener to the SystemTray. The only listener that is supported, is the PropertyChangedListener.
Furthermore from that question it seems to be possible on Windows but not on Linux and MacOS.

This is possible, but not using Java. You'll have to use JNI to access OS APIs that provide this information (and implent it differently for each OS).

Intercept / Disable System Keys in Java

Is there a way to intercept the system keys in Java so that the events are not propagated to the operating system? Ctrl+Alt+Del or other security related combinations do not matter, the main problem is for example the Windows key.
The program in question is a for a full screen application that performs some remote operations via a proprietary protocol. Currently my only idea would be to solve this via JNI, whereas the solution for Windows seems to be simple, I'm not sure about Linux and MAC OS X.
I'd prefer a somewhat standard solution, maybe there is something for Java games or so.

Java processes the key strokes after the operating system (OS), so Java can't "intercept" them. Although, you could code OS specific stuff in C/C++ that intercepted the keystrokes and call it in Java using JNI.

This appears to be fixed in Java 5, so you could have a shot at it. Apparently, the KeyEvent class in the Java API exposes two Microsoft Windows keyboard specific events - VK_WINDOWS (for the left and right winkeys) and VK_CONTEXT_MENU (for the context menu key).
It is quite possible to trap these events by implementing a KeyListener, but be forewarned that if you attempt to capture the Winkey event alone, you're bound to trip the event handler of the OS first, before Java can process it.

Logging Key and Mouse events in java

I would like to capture key strokes and mouse events being entered into a different window, eg such as a browser. What is the best approach to doing this, and no i dont want to be sneaky and capture bank account passwords.
I appreciate that this requires JNI in order to setup some hooks and the like with the current host OS. I could not find any premade java library that had this facility which is odd given that Java has libraries for everything.

This kind of job is OS dependent and there is no cross-platform way to do it with Java.

Is there a way for a Java application to detect if the screen is locked?

I'm looking for a way to know in a Java application (without JNI - it's a multi-platform application) can detect if the screen is locked.
For information... our application records time while a user is working - we want it to automatically stop recording when the screen is locked instead of the user having to do so explicitly.

I don't think there is an API for that or even a way to do it all. Parsing screenshots generated by java.awt.Robot is neither platform- nor version- or even configuration-independant, and in general, I don't think "screen is locked" is a well-enough defined concept to be used in this sense - on Linux, there can be more than just one "screen" (X server), you can switch to console terminals, you can have applications running one (or more) machines display their GUIs on another machine over the network...

I confirm there seems to be no Java API to detect a screen lock status.
Spark developer gave it a try in 2006 (like this thread shows), but without giving out any details on the specific of the implementation.
However, it is likely it involved JNI and native call to functions like WTSQuerySessionInformation (To detect if disconnected use WTSQuerySessionInformation(NULL, WTS_CURRENT_SESSION, WTSConnectState) and look for WTSDisconnected).
So, as Michael pointed out, there is no "multi-platform" universal answer (to the best of my knowledge).