public static void checkNullOrNonNullNonEmptyEntries(
      @Nullable Collection<String> values, String propertyName) {
    if (values == null) {
      // pass
      return;
    }
    for (String value : values) {
      Preconditions.checkNotNull(
          value, "Property '" + propertyName + "' cannot contain null entries");
      Preconditions.checkArgument(
          !value.trim().isEmpty(), "Property '" + propertyName + "' cannot contain empty strings");
    }
  }
@Test
  public void testCheckNullNonNullNonEmptyEntries_valuesPass() {
    Validator.checkNullOrNonNullNonEmptyEntries(ImmutableList.of("first", "second"), "test");
    // pass
  }