Java 子网划分算法实现 - 按需分配构造超网

import java.io.*;

public class Subnetting { /** * @param args */ public static void main(String[] args) throws IOException { // TODO Auto-generated method stub String ip; //用于接收要划分的IP int s; //用于接收以要划分的子网数

    System.out.println('---------------划分子网---------------');
    //输入要划分的IP地址:ip
    System.out.println('请输入要划分的IP地址(格式为：x1.x2.x3.x4)：');
    System.out.print('→:');
    InputStreamReader isr = new InputStreamReader(System.in);
    BufferedReader br = new BufferedReader(isr);
    ip = br.readLine();

    //截取x1
    int index1 = ip.indexOf('.');
    String st1 = ip.substring(0, index1);
    int x1 = Integer.parseInt(st1);//把String类型的st转化成int型

    //截取x2
    int index2 = ip.indexOf('.', index1 + 1);
    String st2 = ip.substring(index1 + 1, index2);
    int x2 = Integer.parseInt(st2);//把String类型的st转化成int型

    //截取x3
    int index3 = ip.indexOf('.', index2 + 1);
    String st3 = ip.substring(index2 + 1, index3);
    int x3 = Integer.parseInt(st3);//把String类型的st转化成int型

    //判断IP类型
    int mask = 0;
    if (x1 >= 0 && x1 <= 127) {
        System.out.println('本IP地址为A类地址，能划分的最大子网数为: ' + ((int) Math.pow(2, 24 - 2) - 2));
        mask = 8;
    } else if (x1 >= 128 && x1 <= 191) {
        System.out.println('本IP地址为B类地址，能划分的最大子网数为: ' + ((int) Math.pow(2, 16 - 2) - 2));
        mask = 16;
    } else if (x1 >= 192 && x1 <= 223) {
        System.out.println('本IP地址为C类地址，能划分的最大子网数为: ' + ((int) Math.pow(2, 8 - 2) - 2));
        mask = 24;
    } else {
        System.out.println('该IP地址不是A、B、C类地址！');
        System.exit(0);
    }

    //输入要划分的子网数数:s
    System.out.println('请输入要划分的子网数：');
    System.out.print('→:');

    String subnet_num = br.readLine();
    s = Integer.parseInt(subnet_num);
    br.close();

    //求所输入子网数对应的二进制位数:n
    int n = (int) Math.ceil(Math.log(s + 2) / Math.log(2));

    //求子网掩码
    int sum = 0;
    for (int i = 0; i < n; i++) {
        sum = sum + (int) Math.pow(2, (7 - i));
    }
    System.out.println('子网掩码为：' + getMask(mask, n));

    //求每网段主机数
    System.out.println('每网段主机数：' + (int) Math.pow(2, (32 - mask - n)) + '个');

    //输出各子网IP范围
    System.out.println('各子网IP范围如下：');
    int subnet_id = 0;
    for (int i = 0; i < s; i++) {
        subnet_id++;
        int sub_id = subnet_id << (32 - mask - n);
        System.out.print('<' + subnet_id + '> ');
        System.out.println(getIP(x1, x2, x3, sub_id) + '---' + getIP(x1, x2, x3, sub_id + (int) Math.pow(2, (32 - mask - n)) - 1));
    }
    System.out.println('子网划分完毕');

}

//获取子网掩码
public static String getMask(int mask, int n) {
    int sum = 0;
    for (int i = 0; i < n; i++) {
        sum = sum + (int) Math.pow(2, (7 - i));
    }
    String[] maskArray = {'0', '128', '192', '224', '240', '248', '252', '254', '255'};
    int index = sum / 8;
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < index; i++) {
        sb.append(maskArray[8]);
        sb.append('.');
    }
    sb.append(maskArray[sum % 8]);
    for (int i = index + 1; i < 4; i++) {
        sb.append('.');
        sb.append(maskArray[0]);
    }
    return sb.toString();
}

//获取IP地址
public static String getIP(int x1, int x2, int x3, int sub_id) {
    int y1 = (sub_id & 0xFF000000) >>> 24;
    int y2 = (sub_id & 0x00FF0000) >>> 16;
    int y3 = (sub_id & 0x0000FF00) >>> 8;
    int y4 = (sub_id & 0x000000FF);
    return x1 + '.' + x2 + '.' + x3 + '.' + y4;
}

}