code: private Collection<String> getPreferredConnections(ModeledAuthenticatedUser user,
              Collection<String> identifiers) {
  
          // Search provided identifiers for any preferred connections
          for (String identifier : identifiers) {
  
              // If at least one prefferred connection is found, assume it is the
              // only preferred connection
              if (user.isPreferredConnection(identifier))
                  return Collections.singletonList(identifier);
  
          }
  
          // No preferred connections were found
          return identifiers;
  
      }
docs: Filters the given collection of connection identifiers, returning a new
  collection which contains only those identifiers which are preferred. If
  no connection identifiers within the given collection are preferred, the
  collection is left untouched.
  
  @param user
  The user whose preferred connections should be used to filter the
  given collection of connection identifiers.
  
  @param identifiers
  The collection of connection identifiers that should be filtered.
  
  @return
  A collection of connection identifiers containing only the subset of
  connection identifiers which are also preferred or, if none of the
  provided identifiers are preferred, the original collection of
  identifiers.