code: public String differenceBetweenAnd(String first, String second) {
          Formatter whitespaceFormatter = new Formatter() {
              @Override
              public String format(String value) {
                  return ensureWhitespaceVisible(value);
              }
          };
          return getDifferencesHtml(first, second, whitespaceFormatter);
      }
docs: Determines difference between two strings.
  @param first first string to compare.
  @param second second string to compare.
  @return HTML of difference between the two.