Review

class CodeGenerator {
  private static void appendHexJavaScriptRepresentation(
      int codePoint, Appendable out)
      throws IOException {
    if (Character.isSupplementaryCodePoint(codePoint)) {
      // Handle supplementary unicode values which are not representable in
      // javascript.  We deal with these by escaping them as two 4B sequences
      // so that they will round-trip properly when sent from java to javascript
      // and back.
      char[] surrogates = Character.toChars(codePoint);
      appendHexJavaScriptRepresentation(surrogates[0], out);
      appendHexJavaScriptRepresentation(surrogates[1], out);
      return;
    }
    out.append("\\u")
        .append(HEX_CHARS[(codePoint >>> 12) & 0xf])
        .append(HEX_CHARS[(codePoint >>> 8) & 0xf])
        .append(HEX_CHARS[(codePoint >>> 4) & 0xf])
        .append(HEX_CHARS[codePoint & 0xf]);
  }

}