code: protected void setNames(Set<String> names)
     {
        this.names.clear();
        this.indexes.clear();
        this.names.addAll(names);
        this.indexes.addAll(names);
        // new list of indexes if thought to be up to date
        dirty = false;
     }
docs: Sets new names, clearing existing. It is thought to be used when list of indexes can
  be externally changed.
  
  @param names