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 int[] tongji = new int[8];
    static int A = 0;
    static int B = 1;
    static int C = 2;
    static int D = 3;
    static int E = 4;
    static int ERROR = 5;
    static int P = 6;
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String[] str = in.nextLine().split("~");
            if (str[0].startsWith("0") || str[0].startsWith("127")) continue;
            if (!isYanMA(str[1]) || !isIp(str[0])) {
                tongji[ERROR]++;
                continue;
            }
            
            tongjiIp(str[0]);
        }
        StringBuffer sb = new StringBuffer();
        sb.append(tongji[0]);
        for (int i = 1; i < 7; i++) {
            sb.append(" ").append(tongji[i]);
        }
        System.out.println(sb.toString());
    }
    public static void tongjiIp(String ip) {
        if (ip.startsWith("0") || ip.startsWith("127")) return;
        if (!isIp(ip)) return;
        String[] ipArray = ip.split("\\.");
        int temp = Integer.parseInt(ipArray[0]);
        if (temp >= 1 && temp <= 126) tongji[A]++;
        if (temp >= 128 && temp <= 191) tongji[B]++;
        if (temp >= 192 && temp <= 223) tongji[C]++;
        if (temp >= 224 && temp <= 239) tongji[D]++;
        if (temp >= 240 && temp <= 255) tongji[E]++;
        if (temp == 10) tongji[P]++;
        int temp2 = Integer.parseInt(ipArray[1]);
        if (temp == 172 && (temp2 >= 16 && temp2 <= 31)) tongji[P]++;
        if (ip.startsWith("192.168")) tongji[P]++;
    }
    public static boolean isIp(String ip) {
        String[] ipArray = ip.split("\\.");
        for (String tt : ipArray) {
            if (tt.equals("")) return false; 
            int temp = Integer.parseInt(tt);
            if (temp < 0 && temp > 255) return false;
        }
        return true;
    }
    public static boolean isYanMA(String str) {
        if(str.equals("0.0.0.0") || str.equals("255.255.255.255")) return false;
        String[] ipArray = str.split("\\.");
        StringBuffer sb = new StringBuffer();
        for (String tt : ipArray) {
            int temp = Integer.parseInt(tt);
            if (temp < 0 && temp > 255) return false;
            String tempBin = Integer.toString(temp, 2);
            if (tempBin.length() < 8) {
                for (int i = 0; i < 8 - tempBin.length(); i++) {
                    sb.append("0");
                }
            }
            sb.append(tempBin);
        }
        String IpString = sb.toString();
        int index0 = IpString.indexOf('0');
        for (int i = index0; i < IpString.length(); i++) {
            if(IpString.charAt(i) == '1') return false;
        } 
        return true;
    }
}