code: static UnionImpl initNewHeapInstance(final int lgNomLongs, final long seed, final float p,
        final ResizeFactor rf) {
      final UpdateSketch gadget = new HeapQuickSelectSketch(
          lgNomLongs, seed, p, rf, true); //create with UNION family
      final UnionImpl unionImpl = new UnionImpl(gadget, seed);
      unionImpl.unionThetaLong_ = gadget.getThetaLong();
      unionImpl.unionEmpty_ = gadget.isEmpty();
      return unionImpl;
    }
docs: Construct a new Union SetOperation on the java heap.
  Called by SetOperationBuilder.
  
  @param lgNomLongs <a href="{@docRoot}/resources/dictionary.html#lgNomLogs">See lgNomLongs</a>
  @param seed <a href="{@docRoot}/resources/dictionary.html#seed">See seed</a>
  @param p <a href="{@docRoot}/resources/dictionary.html#p">See Sampling Probability, <i>p</i></a>
  @param rf <a href="{@docRoot}/resources/dictionary.html#resizeFactor">See Resize Factor</a>
  @return instance of this sketch