code: public static boolean isIdentifierIgnorable(int ch)
      {
          // see java.lang.Character.isIdentifierIgnorable() on range of
          // ignorable characters.
          if (ch <= 0x9f) {
              return isISOControl(ch)
                      && !((ch >= 0x9 && ch <= 0xd)
                              || (ch >= 0x1c && ch <= 0x1f));
          }
          return getType(ch) == UCharacterCategory.FORMAT;
      }
docs: Determines if the specified code point should be regarded as an
  ignorable character in a Java identifier.
  A character is Java-identifier-ignorable if it has the general category
  Cf Formatting Control, or it is a non-Java-whitespace ISO control:
  U+0000..U+0008, U+000E..U+001B, U+007F..U+009F.<br>
  Up-to-date Unicode implementation of
  java.lang.Character.isIdentifierIgnorable().<br>
  See <a href=http://www.unicode.org/unicode/reports/tr8/>UTR #8</a>.
  <p>Note that Unicode just recommends to ignore Cf (format controls).
  @param ch code point to be determined if it can be ignored in a Unicode
  identifier.
  @return true if the code point is ignorable