private void scanCategories(){
  presetCategories.clear();
  for (  AddressbookEntry entry : entries.values()) {
    addPresetCategories(entry.getCategories());
  }
}

private void scanCategories ( ) { presetCategories . clear ( ) ; for ( AddressbookEntry entry : entries . values ( ) ) { addPresetCategories ( entry . getCategories ( ) ) ; } }
goes through all entries and adds all found categories to a set .
