private void initializePossibleAttributeNames ( ) { final Set < String > possibleAttribNames = new LinkedHashSet <> ( ) ; for ( final Map < String , List < Object > > attributeMapForSomeUser : this . backingMap . values ( ) ) { final Set < String > keySet = attributeMapForSomeUser . keySet ( ) ; possibleAttribNames . addAll ( keySet ) ; } this . possibleUserAttributeNames = Collections . unmodifiableSet ( possibleAttribNames ) ; }
Compute the set of attribute names that map to a value for at least one user in our backing map and store it as the instance variable possibleUserAttributeNames .