utf8 的字串還原成 \uxxxx

public static String ChineseToUnicode(String s) {
StringBuffer bu = new StringBuffer(s);
String unicode = "";
for(int i = 0; i < bu.length(); i++) {
String tmp = Integer.toHexString((int)bu.charAt(i));
unicode = unicode + "\\u" + tmp;
}
return unicode;
}