private static void checkSurrogatePair(CharSequence value, int offset, int len) { char hi = value.charAt(offset); if (len <= offset) throw new RuntimeException( String.format("Character sequence ends with single surrogate character: 0x%X", hi)); char lo = value.charAt(offset + 1); if (!Character.isSurrogatePair(hi, lo)) throw new RuntimeException(String.format("Malformed surrogate pair: 0x%X - 0x%X", hi, lo)); }