code: public static StringBuilder camelCase(final StringBuilder target, boolean firstToLower, final String... tokens) {
          for (String t: tokens) {
              if (firstToLower) {
                  firstToLower = false;
                  target.append(t.toLowerCase());
              } else {
                  appendFirstToUpper(target, t);
              }
          }
          return target;
      }
docs: Appends {@code tokens} to {@code target} in CamelCase format.
  @param tokens parts of the word
  @param target string builder the word is appended to
  @param firstToLower if true, the first character will be in lowercase