decorate a comboBox so that it remembers recent entries. This listens for ActionEvents from a JComboBox and adds valid items to its droplist. The recent entries are stored in the bookmarks folder in the file "recent.PREF.txt" where PREF is a string assigned to this object identifying the theme, such as "timerange". Specifically, the event is validated and recorded into the file, then the file is loaded, sorted, and saved again.
add the item to the list of recent entries. This will reload the recent file, probably firing events.
get the string value, which is also the getSelectedItem. This will also push a changed value to the recent entries.
check if the human has made modifications to this value.
associate the history with a file. This should be called immediately after creating the object.
to make it easier to convert GUIs with JTextFields to RecentComboBoxes, setText is available.
allow filtering of invalid entries so they aren't recorded in history.