题解 | 识别有效的IP地址和掩码并进行分类统计

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int a = 0;
        int b = 0;
        int c = 0;
        int d = 0;
        int e = 0;
        int pri = 0;
        int error = 0;

        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String str = in.nextLine();
            String[] IPs = str.split("~");
            boolean isE = true;

            //判断IP是否合法
            String[] IP = IPs[0].split("\\.");
            
            if (IP[0].equals("0") || IP[0].equals("127")) {
                continue;
            }
            for (int i = 0; i <= 3; i++) { //判断是否有空
                if (IP[i].equals("")) {
                    isE = false;
                    break;
                }
            }
            if (!isE) {
                error++;
                continue;
            }

            //子网掩码是否合法
            String[] ips = IPs[1].split("\\.");
            for (int i = 0; i <= 3; i++) {  //判断是否有空
                if (ips[i].equals("")) {
                    isE = false;
                    break;
                }
            }
            if (!isE) {
                error++;
                continue;
            }

            int[] part = new int[4];  //存放十进制
            String ziW = new String();  //存放二进制子网掩码
            for (int i = 0; i <=3; i++) {  //进制转换
                part[i] = Integer.parseInt(ips[i]);
                ips[i] = String.format("%8s",Integer.toBinaryString(part[i])).replace(' ', '0');  //转换成二进制
                ziW = ziW + ips[i];
            }
            
            int index0 = ziW.indexOf('0');
            int index1 = ziW.indexOf('1');
            if (index0 == -1 || index1 == -1) {
                error++;
                continue;
            }
            String ziWChange = ziW.substring(index0);
            if (ziWChange.indexOf('1') >= 0) {
                error++;
                continue;
            }

            //判断IP是哪一类
            int ten = Integer.parseInt(IP[0]);
            int ten2 = Integer.parseInt(IP[1]);
            if (ten >= 1 && ten <= 127) {
                a++;
            } else if (ten >= 128 && ten <= 191) {
                b++;
            } else if (ten >= 192 && ten <= 223) {
                c++;
            } else if (ten >= 224 && ten <= 239) {
                d++;
            } else {
                e++;
            }
            if (ten == 10) {
                pri++;
            } else if (ten == 172 && ten2 >= 16 && ten2 <= 31) {
                pri++;
            } else if (ten == 192 && ten2 == 168) {
                pri++;
            }
        }
        System.out.print(a + " " + b +" "+c+" "+d+" "+e+" "+error+" "+pri);
    }
}