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);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String a = in.nextLine();
            long b = Long.parseLong(in.nextLine());
            System.out.println(ipToLong(a));
            System.out.println(longToIp(b));
        }
    }

    public static long ipToLong(String ip) {
        String[] array = ip.split("\\.");
        long sum = (Long.parseLong(array[0])<<24) + (Long.parseLong(array[1])<<16) + (Long.parseLong(array[2])<<8) + (Long.parseLong(array[3]));
        return sum;
    }

    public static String longToIp(long sum) {
        long n4 = (sum>>24);
        sum -= (n4<<24);
        long n3 = (sum)>>16;
        sum -= (n3<<16);
        long n2 = (sum)>>8;
        sum -= (n2<<8);
        long n1 = sum;
        String ip = "" + n4 + "." + n3 + "." + n2 + "." + n1;
        return ip;
     }
}