题解HJ33 | #整数与IP地址间的转换#

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);
        String input1 = in.nextLine();
        String input2 = in.nextLine();
        String[] strings = input1.split("\\.");
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i < strings.length; i++) {
            sb.append(tenToTwo(strings[i], 8));
        }
	 
	 //注意这里是Long
        System.out.println(Long.valueOf(sb.toString(), 2).toString());
        System.out.println(twoToTen(input2));
    }

    //二进制转十进制
    private static String twoToTen(String str) {
        // 11100110  10010110  11010000  10011111
        // 00001010  00000011  00000011  11000001
        String totalStr = tenToTwo(str, 32);
        String[] strs = new String[4];
        for (int i = 0; i < 4; i++) {
            strs[i] = totalStr.substring(i * 8, i * 8 + 8);
            // String singleNum = twoToTen(strs[i]);
            String temp = strs[i];
            long num = Long.parseLong(temp, 2);
            strs[i] = String.valueOf(num);
        }
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 4; i++) {
            sb.append(strs[i]);
            if (i != 3) sb.append('.');
        }
        return sb.toString();
    }

    //十进制转二进制
    private static String tenToTwo(String str, int length) {
        long num = Long.parseLong(str, 10);
        StringBuilder sb = new StringBuilder();
        long temp = 0;
        while (num != 0) {
            temp = num % 2;
            num /= 2;
            if (temp == 0) {
                sb.append((char) ('0' + 0));
            } else {
                sb.append((char) ('0' + 1));
            }
        }
        int len = sb.length();
        if (len < length) {
            for (int i = 0; i < length - len; i++) {
                sb.append('0');
            }
        }
        return sb.reverse().toString();
    }
}

好麻烦