//將127.0.0.1形式的IP地址轉換成十進位制整數，這裡沒有進行任何錯誤處理  
     public static long ipToLong(String strIp){  
         long[] ip = new long[4];  
         //先找到IP地址字串中.的位置  
         int position1 = strIp.indexOf(".");  
         int position2 = strIp.indexOf(".", position1 + 1);  
         int position3 = strIp.indexOf(".", position2 + 1);  
         //將每個.之間的字串轉換成整型  
         ip[0] = Long.parseLong(strIp.substring(0, position1));  
         ip[1] = Long.parseLong(strIp.substring(position1+1, position2));  
         ip[2] = Long.parseLong(strIp.substring(position2+1, position3));  
         ip[3] = Long.parseLong(strIp.substring(position3+1));  
         return (ip[0] << 24) + (ip[1] << 16) + (ip[2] << 8) + ip[3];  
     }  
       
     //將十進位制整數形式轉換成127.0.0.1形式的ip地址  
     public static String longToIP(long longIp){  
         StringBuffer sb = new StringBuffer("");  
         //直接右移24位  
         sb.append(String.valueOf((longIp >>> 24)));  
         sb.append(".");  
         //將高8位置0，然後右移16位  
         sb.append(String.valueOf((longIp & 0x00FFFFFF) >>> 16));  
         sb.append(".");  
         //將高16位置0，然後右移8位  
         sb.append(String.valueOf((longIp & 0x0000FFFF) >>> 8));  
         sb.append(".");  
         //將高24位置0  
         sb.append(String.valueOf((longIp & 0x000000FF)));  
         return sb.toString();  
     } 

public static void main(String[] args) throws ParseException {

String[] ipStrs = {"192.168.54.21","192.168.54.15","192.168.54.17","192.168.54.18","192.168.54.19","192.168.54.31"};
         for (int i = 0; i < ipStrs.length; i++) {
    String ipStri = ipStrs[i];
    long longIp = ipToLong(ipStri);  
          System.out.println("192.168.0.1 的整數形式為：" + longIp);  
          System.out.println("整數" + longIp + "轉化成字串IP地址：" 
                  + longToIP(longIp));
   }

}