Imagine this: You make a simple game using a contained within a JFrame. The game is played by moving your mouse around and clicking on different things.
Can you then make a virtual mouse to interact with that game that will not interfere with your normal cursor actions, and only do things within the JFrame. Like you could browse the web while it is running and it wouldn't interfere.
Note: This has nothing to do with interacting with the game objects in code directly, but simple a virtual mouse overlay to interact with it in a simulated way.
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This was also mention in a similar thread here: Need an alternative to java.awt.Robot