How to track motion from a moving hand in Java?

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Hello People, I'm new to OpenCV, but have a lot of experience in Java coding. As Java support is quite new, I haven't found any suitable information on what I need.

I am part of a small group which wants to build a little gadget, which automatically refills glasses with shooting the watter into them. We want to mount a camera 1-2 meters above the table, to track the position of the glasses and look for a hand gesture which shall be the signal to refill the glass.

I looked through the tutorials but couldn't find something suitable. I'd be glad if someone could tell me roughly how to do it, and which classes I need to use, and what for. Or, of course, show me a tutorial which does exactly that.

Thanks in advance,

Zero