unicode转码，如：\u6d4b\u8bd5转成中文“测试”

 　　public static void main(String[] args) {
         String s = "测试";
         String tt = gbEncoding(s); // String tt1 = "你好，我想给你说一个事情";
         System.err.println(s + " to unicode :" + tt);
         System.err.println(tt + " decode unicode :" + decodeUnicode(tt));
     }

     public static String gbEncoding(final String gbString) {
         char[] utfBytes = gbString.toCharArray();
         String unicodeBytes = "";
         for (int byteIndex = 0; byteIndex < utfBytes.length; byteIndex++) {
             String hexB = Integer.toHexString(utfBytes[byteIndex]);
             if (hexB.length() <= 2) {
                 hexB = "00" + hexB;
             }
             unicodeBytes = unicodeBytes + "\\u" + hexB;
         }
         return unicodeBytes;
     }

     public static String decodeUnicode(final String dataStr) {
         int start = 0;
         int end = 0;
         final StringBuffer buffer = new StringBuffer();
         while (start > -1) {
             end = dataStr.indexOf("\\u", start + 2);
             String charStr = "";
             if (end == -1) {
                 charStr = dataStr.substring(start + 2, dataStr.length());
             } else {
                 charStr = dataStr.substring(start + 2, end);
             }
             char letter = (char) Integer.parseInt(charStr, 16); // 16进制parse整形字符串。
             buffer.append(new Character(letter).toString());
             start = end;
         }
         return buffer.toString();
     }