public static String unescape(String s) {
        int len = s.length();
        StringBuffer b = new StringBuffer();
        for (int i = 0; i < len; ++i) {
            char c = s.charAt(i);
            if (c == '+') {
                c = ' ';
            } else if (c == '%' && i + 2 < len) {
                int d = JSONTokener.dehexchar(s.charAt(i + 1));
                int e = JSONTokener.dehexchar(s.charAt(i + 2));
                if (d >= 0 && e >= 0) {
                    c = (char)(d * 16 + e);
                    i += 2;
                }
            }
            b.append(c);
        }
        return b.toString();
    }