第六章第三十四题（打印日历）(Print calendar) - 编程练习题答案

// https://cn.fankuiba.com
import java.util.Scanner;

public class Ans6_34_page205 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter full year (e.g., 2012): ");
        int year = input.nextInt();
        System.out.print("What day is January 1, "+year+" ? ");
        int week = input.nextInt();

        int month = 1, day = 0;
        String monthString = "";
        boolean leapYear;

        if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0 && year % 3200 != 0) || year % 172800 == 0)
            leapYear = true;
        else
            leapYear = false;

        for (; month <= 12; month++) {
            switch (month) {
                case 1:
                    monthString = "January";
                    break;
                case 2:
                    day += 31;
                    monthString = "February";
                    break;
                case 3:
                    monthString = "March";
                    if (leapYear)
                        day += 29;
                    else
                        day += 28;
                    break;
                case 4:
                    day += 31;
                    monthString = "April";
                    break;
                case 5:
                    day += 30;
                    monthString = "May";
                    break;
                case 6:
                    day += 31;
                    monthString = "June";
                    break;
                case 7:
                    day += 30;
                    monthString = "July";
                    break;
                case 8:
                    day += 31;
                    monthString = "August";
                    break;
                case 9:
                    day += 31;
                    monthString = "September";
                    break;
                case 10:
                    day += 30;
                    monthString = "October";
                    break;
                case 11:
                    day += 31;
                    monthString = "November";
                    break;
                case 12:
                    day += 30;
                    monthString = "December";
            }
            int days = (week + day) % 7;
            System.out.print("\n           " + monthString + " " + year + "\n---------------------------------");
            System.out.printf("\n%-5s%-5s%-5s%-5s%-5s%-5s%-5s\n", "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat");

            for (int n =1;n<=days;n++) {
                System.out.printf("%-5s", "");
            }

            int j = 1;
            if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 ||
                    month == 12) {
                for (; j <= 31; j++) {
                    System.out.printf("%-5d", j);
                    if ((days+j) % 7 == 0)
                        System.out.println();
                }
            }
            else if (month == 2 && leapYear) {
                for (; j <= 29; j++) {
                    System.out.printf("%-5d", j);
                    if ((days+j) % 7 == 0)
                        System.out.println();
                }
            }
            else if (month == 2) {
                for (; j <= 28; j++) {
                    System.out.printf("%-5d", j);
                    if ((days+j) % 7 == 0)
                        System.out.println();
                }
            }
            else {
                for (; j <= 30; j++) {
                    System.out.printf("%-5d", j);
                    if ((days + j) % 7 == 0)
                        System.out.println();
                }
            }
            System.out.print("\n");
            switch (days) {
                case 0:
                    System.out.print("Sun");break;
                case 1:
                    System.out.print("Mon");break;
                case 2:
                    System.out.print("Tue");break;
                case 3:
                    System.out.print("Wed");break;
                case 4:
                    System.out.print("Thu");break;
                case 5:
                    System.out.print("Fri");break;
                case 6:
                    System.out.print("Sat");
            }
            System.out.println(" starts on the first day of "+monthString);
        }
    }
}