判断两个Ip地址是否同属一个子网-Java

import java.util.*;

public class PanDuanIpTongZiWang {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            String yanMa = sc.next();
            String ip1 = sc.next();
            String ip2 = sc.next();
            if (goodYanMa(yanMa) && goodIp(ip1) && goodIp(ip2)) {
                if ((change(yanMa) & change(ip1)) == (change(yanMa) & change(ip2)))
                    System.out.println("Ip1与Ip2同属一个子网");
                else
                    System.out.println("Ip1与Ip2不属一个子网");
            } else
                System.out.println("不合法的Ip或子网掩码");
        }
    }

    public static long change(String s) { //将十进制分组的Ip，转为十进制不分组的Ip，以方便后续和子网掩码进行&运算
        String[] split = s.split("\\.");
        StringBuilder builder = new StringBuilder();
        for (String s1 : split) {
            String s2 = Long.toString(Long.parseLong(s1), 2);
            while (s2.length() != 8) {
                s2 = new StringBuilder(s2).insert(0, 0).toString();
            }
            builder.append(s2);
        }
        return Long.valueOf(builder.toString(), 2);
    }

    public static boolean goodIp(String s) { //判断Ip是否合法
        String[] split = s.split("\\.");
        if (split.length!=4)
            return false;
        for (String s1 : split) {
            if (Integer.parseInt(s1) < 0 || Integer.parseInt(s1) > 255) {
                return false;
            }
        }
        return true;
    }

    public static boolean goodYanMa(String s) { //判断子网掩码是否合法
        String[] split = s.split("\\.");
        if (split.length != 4)
            return false;
        StringBuilder builder = new StringBuilder();
        for (String s1 : split) {
            if (Integer.parseInt(s1) >= 0 && Integer.parseInt(s1) <= 255) { //若不在0-255之间，则返回false
                String s2 = Long.toString(Long.parseLong(s1), 2); //每组转为二进制
                while (s2.length() != 8) { //若转为二进制之后，长度不够8位，需要在前面补全0
                    s2 = new StringBuilder(s2).insert(0, 0).toString();
                }
                builder.append(s2);
            } else {
                return false;
            }
        }
        String toString = builder.toString();
        if (toString.equals("11111111111111111111111111111111") || toString.equals("00000000000000000000000000000000")) { //全1或者全0的子网掩码也是不合法的
            return false;
        }
        for (int i = 0; i < toString.length() - 1; i++) {
            String substring = toString.substring(i, i + 2);
            if (substring.equals("01")) {//如何判断子网掩码是否合法，在最后拼接好的32位二进制字符串中查找，是否包含“01”，若包含则不合法
                return false;
            }
        }
        return true;
    }
}