See the email http://mail.openjdk.java.net/pipermail/swing-dev/2014-December/004085.html
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The fix looks good. The root cause of this error is that mouseExited is not fired on the focused container when a modal dialog is shown. I'm surprised that there isn't a linked issue against AWT to either fix the toolkit to fire the mouseExited (via the Z axis) on modal dialog, suppress the 2nd call to mouseEntered after dialog is closed, or fix the MousListener documentation to state that how the mouse cursor enters or leaves a component has some exceptional conditions. My preference would be to fire mouseExited on modal dialog shown.
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