// hello world xiao hong >>> hong xiao world   hello
     public static String conversionStr(String string)
     {
         if (string == null || "".equals(string))
             return null;
         String[] arrStr = string.split(" ");
         StringBuilder sb = new StringBuilder(string
 
.length());
         for (int i=arrStr.length-1;i>=0;i--)
         {
             sb.append(arrStr[i]).append(" ");
         }

         return sb.toString();
     }