Java 获取子网掩码

import java.util.*;import java.net.*;public class SubnetMask {    public static void main(String[] args) {        InetAddress ip = null;        NetworkInterface ni = null;        try {            ip = InetAddress.getLocalHost();            ni = NetworkInterface.getByInetAddress(ip);// 搜索绑定了指定IP地址的网络接口        } catch (Exception e) {            e.printStackTrace();        }        List<InterfaceAddress> list = ni.getInterfaceAddresses();// 获取此网络接口的全部或部分                                                                    // InterfaceAddresses                                                                    // 所组成的列表        if (list.size() > 0) {            int mask = list.get(0).getNetworkPrefixLength(); // 子网掩码的二进制1的个数            StringBuilder maskStr = new StringBuilder();            int[] maskIp = new int[4];            for (int i = 0; i < maskIp.length; i++) {                maskIp[i] = (mask >= 8) ? 255 : (mask > 0 ? (mask & 0xff) : 0);                mask -= 8;                maskStr.append(maskIp[i]);                if (i < maskIp.length - 1) {                    maskStr.append(".");                }            }            System.out.println("SubnetMask:" + maskStr);        }    }}