Using AutoCompleteSupport in a JComboBox will result in a NPE in the following
Pressing a button opens a panel with a JComboBox with AutoCompleteSupport
installed, the combobox get's first focus.
Pressing the button using [ENTER] will, if you don't release [ENTER] quick
enough, result in AutoCompleteKeyHandler handling a keyReleased event, which
assumes keyPressed has been called (setting up the array of listeners).
Therefore you get a NullPointerEception.