ava字符串长度截取 考虑汉字

 public static String getLimitLengthString( String str,int len){      try{      int counterOfDoubleByte = 0;      byte[] b = str.getBytes("gb2312");      if(b.length <= len)      return str;      for(int i = 0; i < len; i++){      if(b[i] < 0)      counterOfDoubleByte++;      }      if(counterOfDoubleByte % 2 == 0)      return new String(b, 0, len, "gb2312");      else      return new String(b, 0, len - 1, "gb2312");      }catch(Exception ex){      DBTools.error(ex);      return "";      }      }