* Returns a splitter that uses the given single-character separator. For example, {@code
   * Splitter.on(',').split("foo,,bar")} returns an iterable containing {@code ["foo", "", "bar"]}.
   *
   * @param separator the character to recognize as a separator
   * @return a splitter, with default settings, that recognizes that separator
   */
  public static Splitter on(char separator) {
    return on(CharMatcher.is(separator));
  }

   * Returns a splitter that uses the given single-character separator. For example, {@code
   * Splitter.on(',').split("foo,,bar")} returns an iterable containing {@code ["foo", "", "bar"]}.
   *
   * @param separator the character to recognize as a separator
   * @return a splitter, with default settings, that recognizes that separator
   */
  public static Splitter on(char separator) {
    return on(CharMatcher.is(separator));
  }