question: private boolean haveShownMessageBefore ( UpdateMessage msg ) { if ( ! msg . isShownOnce ( ) ) return false ; loadSeenMessages ( ) ; if ( _seenMessages == null || _seenMessages . size ( ) == 0 || ! _seenMessages . contains ( msg ) ) { if ( _seenMessages == null ) _seenMessages = new HashSet < > ( ) ; _seenMessages . add ( msg ) ; saveSeenMessages ( ) ; return false ; } return true ; }
target:  Checks on a Message map, if we've seen this message before. The message map is serialized on disk every time we write to it. Its initialized from disk when we start the Update Manager.