题解 | #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 line = in.nextLine();
            String out = "";
            if (line.contains(".")) {
                String[] len8 = line.split("\\.");
                System.out.println((Long.parseLong(len8[0]) << 24) +
                                   (Long.parseLong(len8[1]) << 16) +
                                   (Long.parseLong(len8[2]) << 8) +
                                   (Long.parseLong(len8[3])));
            } else {
                Long num = Long.parseLong(line);
                System.out.println((num >> 24) + "." + (num >> 16 & 255) + "." +
                                   (num >> 8 & 255) + "." + (num & 255));
            }
        }
    }

}