public FeatureSet combine(final FeatureSet other){
  final Set<Feature> enabled=new HashSet<>(this.enabled);
  enabled.addAll(other.enabled);
  final Set<Feature> disabled=new HashSet<>(this.disabled);
  disabled.addAll(other.disabled);
  return new FeatureSet(enabled,disabled);
}

public FeatureSet combine ( final FeatureSet other ) { final Set < Feature > enabled = new HashSet < > ( this . enabled ) ; enabled . addAll ( other . enabled ) ; final Set < Feature > disabled = new HashSet < > ( this . disabled ) ; disabled . addAll ( other . disabled ) ; return new FeatureSet ( enabled , disabled ) ; }
combine this feature set with another .
