@Udf
  public String concat(@UdfParameter(
      description = "The varchar fields to concatenate") final String... inputs) {
    if (inputs == null) {
      return null;
    }

    return Arrays.stream(inputs)
        .filter(Objects::nonNull)
        .collect(Collectors.joining());
  }
@Test
  public void shouldConcatStrings() {
    assertThat(udf.concat("The", "Quick", "Brown", "Fox"), is("TheQuickBrownFox"));
  }