protected SetBase<T> unsetFeature(C.Feature feature) { features_().remove(feature); return this; }
protected SetBase<T> setFeature(C.Feature feature) { features_().add(feature); return this; }
protected SetBase<T> unsetFeature(C.Feature feature) { features_().remove(feature); return this; }
@Override public final boolean is(C.Feature feature) { return features_().contains(feature); }
@Override public final EnumSet<C.Feature> features() { return EnumSet.copyOf(features_()); }
@Override public final boolean is(C.Feature feature) { return features_().contains(feature); }
@Override public final EnumSet<C.Feature> features() { return EnumSet.copyOf(features_()); }
protected SetBase<T> setFeature(C.Feature feature) { features_().add(feature); return this; }