Homework_7

//노재경

import java.time.LocalDate;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        int year = 0;
        int month = 0;
        Scanner scanner = new Scanner(System.in);
        
        boolean yearCheck = true;
        boolean monthCheck = true;
        
        // 사용자로부터 년도와 월을 입력 받음
        while(yearCheck) {
            System.out.println("[달력 출력 프로그램]");
            System.out.print("달력의 년도를 입력해 주세요.(yyyy): ");
            year = scanner.nextInt();
            if(year < 0) {
                System.out.println("연도는 0 이상이어야 합니다");
            } else {
                yearCheck = false;
            }
        }   

        while(monthCheck) {
            System.out.print("달력의 월을 입력해 주세요.(mm): ");
            month = scanner.nextInt();
            if(month < 1 || month > 12) {
                System.out.println("1부터 12까지의 정수를 입력해주세요");
            } else {
                monthCheck = false;
            }
        }

        printCalendar(year, month);
        scanner.close();
    }

    public static void printCalendar(int year, int month) {

        // 지난달 달력 출력
        int lastYear;
        int lastMonth;
        int lastDate = 1;
        int lastDay;

        if(month == 1) {
            lastYear = year - 1;
            lastMonth = 12;
        } else {
            lastYear = year;
            lastMonth = month - 1;
        }
        LocalDate lastFirstDate = LocalDate.of(lastYear, lastMonth, lastDate); // 날짜 가져오기
        lastDay = lastFirstDate.getDayOfWeek().getValue(); // 요일 가져오기

        System.out.printf("\n[%d년\t%02d월]\n", lastYear, lastMonth);
        System.out.println("일\t월\t화\t수\t목\t금\t토\t");

        for(int i = 0; i < lastDay % 7; i++) {
            System.out.print("\t");
        }
        for(int i = 1; i <= lastFirstDate.lengthOfMonth(); i++) {
            System.out.printf("%02d\t", lastDate++);
            lastDay++;
    
            if(lastDay % 7 == 0) {        
                System.out.println();
            }
        }

        // 이번달 달력 출력
        int date = 1;
        int day;
        LocalDate firstDate = LocalDate.of(year, month, date);
        day = firstDate.getDayOfWeek().getValue(); // 요일 값

        System.out.printf("\n[%d년\t%02d월]\n", year, month);
        System.out.println("일\t월\t화\t수\t목\t금\t토\t");

        for(int i = 0; i < day % 7; i++) {
            System.out.print("\t");
        }
        for(int i = 1; i <= firstDate.lengthOfMonth(); i++) {
            System.out.printf("%02d\t", date++);
            day++;

            if(day % 7 == 0) {
                System.out.println();
            }
        }

        // 다음달 달력 출력
        int nextYear;
        int nextMonth;
        int nextDate = 1;
        int nextDay;

        if(month == 12) {
            nextYear = year + 1;
            nextMonth = 1;
        } else {
            nextYear = year;
            nextMonth = month + 1;
        }
        LocalDate nextFirstDate = LocalDate.of(nextYear, nextMonth, nextDate);
        nextDay = nextFirstDate.getDayOfWeek().getValue();

        System.out.printf("\n[%d년\t%02d월]\n", nextYear, nextMonth);
        System.out.println("일\t월\t화\t수\t목\t금\t토\t");

        for(int i = 0; i < nextDay % 7; i++) {
            System.out.print("\t");
        }
        for(int i = 1; i <= nextFirstDate.lengthOfMonth(); i++) {
            System.out.printf("%02d\t", nextDate++);
            nextDay++;
    
            if(nextDay % 7 == 0) {        
                System.out.println();
            }
        }
    } 
}