escaped html won't unescaped (now: unescaped html won't escape back)

So I'm currently using the commons lang apache library.

When I tried unescaping this string: 😀 This returns the same string: 😀

String characters = "😀"
StringEscapeUtils.unescapeHtml(characters);

Output: 😀

But when I tried unescaping a String with a less few characters, it works:

String characters = "㈳"
StringEscapeUtils.unescapeHtml(characters);

Output: ㈳

Any ideas? When I tried unescaping this String "😀" on online unescaping utility, it works, so maybe it's a bug in the apache common langs library? Or can anyone recommend another library?

Thanks.

UPDATES:

I'm now able to unescape the String successfully. The problem now is when I tried to escaped the result of that unescape, it won't bring back the String (😀).