main.java

import java.util.*;

public class f22aa021_Maeda {
    public static void main(String[] args) {
        // Exception handling with Try Catch System.
        // case to determine the month -> if it is over 12, it is treated as an exception.
        // write by Nknight AMAMIYA.
        try {
            Scanner sc = new Scanner(System.in);
            Integer intake = sc.nextInt();

            String latestMonthDay = switch (intake) {
                case 1 -> "31";
                case 2 -> "28";
                case 3 -> "31";
                case 4 -> "30";
                case 5 -> "31";
                case 6 -> "30";
                case 7 -> "31";
                case 8 -> "31";
                case 9 -> "30";
                case 10 -> "31";
                case 11 -> "30";
                case 12 -> "31";
                default -> "error";
            };
            StringBuilder sb = new StringBuilder();
            if (latestMonthDay.equals("error")) {
                System.out.println("please input value of 1 - 12!");
            } else {
                sb.append(intake+ "is");
                sb.append(latestMonthDay);
                System.out.println(sb);
            }
        } catch (Exception e) {
            System.out.println("input int.");
        }
    }
}

update.