Setting action listener on system applications

How can I set the action listener on system applications?

What I want is: when I start writing on the notepad, my action listener should detect it and I should be able to view what I had typed. The same that happens in a keylogger.

This was just the case of notepad but I want that every time I type something my program should be able to view it.

Example: after opening Chrome, I typed java in the search bar. Now my program's action listener should be able to detect what 开发者_StackOverflowI typed.

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You can't do this in Java alone. Period. You may try JNI, but definitely not in Java alone.