code: public static <T> Stream<T> buildConcatStream(List<T> sample1,
              List<T> sample2) {
          return Stream.concat(sample1.stream(), sample2.stream());
      }
docs: Build concat stream stream.
  
  @param <T>     the type parameter
  @param sample1 the sample 1
  @param sample2 the sample 2
  @return the stream