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Design a program to accept a day number (between 1 and 366), year (in 4 digits) from the user to generate and display the corresponding date. Also, accept ‘N’ (1 <= N <= 100) from the user to compute and display the future date corresponding to ‘N’ days after the generated date. Display an error message if the value of the day number, year and N are not within the limit or not according to the condition specified. 

import java.util.*;

public class NumberToDate {
    int days, year, after;
    private String[] MONTH_NAME = {
            "January", "February", "March", "April", "May", "June", "July", "August", "September", "October",
            "November", "December"
    };

    void input() {
        Scanner sc = new Scanner(System.in);
        System.out.print("Day Number: ");
        days = sc.nextInt();
        System.out.print("Year: ");
        year = sc.nextInt();
        if (year < 1000 || year > 9999) {
            System.out.println("Year should 4 digit number");
            System.exit(0);
        }
        System.out.print("Date After(in days): ");
        after = sc.nextInt();
        if (after < 1 || after > 100) {
            System.out.println("Date After should be between 1 and 100");
            System.exit(0);
        }
        sc.close();
    }

    private String postfix(int n) {
        int r = n % 10;
        if (r == 1 && n != 11)
            return "st";
        else if (r == 2 && n != 12)
            return "nd";
        else if (r == 3 && n != 13)
            return "rd";
        else
            return "th";
    }

    private String date_convert(int n, int y) {
        int max = 365, m = 1, d = 0;
        int[] DAY_COUNT = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
        if (y % 4 == 0) {
            max++;
            DAY_COUNT[1]++;
        }
        while (n > max) {
            n -= max;
            y++;
        }
        while (true) {
            int m_days = DAY_COUNT[m - 1];
            d = n % (m_days + 1);
            n -= m_days;
            if (n > 0) {
                m++;
            } else
                break;
        }
        return String.format("%d%s %s, %d", d, postfix(d), MONTH_NAME[m - 1], y);
    }

    void showDate() {
        System.out.println("Date: " + date_convert(days, year));
    }

    void showAfterDate() {
        System.out.printf("Date After %d Days: %s\n", after, date_convert(days + after, year));
    }

    public static void main(String[] args) {
        NumberToDate a = new NumberToDate();
        a.input();
        a.showDate();
        a.showAfterDate();
    }
}

Algorithm

Algorithm for main() method

  1. Create an object of the class NumberToDate
  2. Invoke the method input() of the object
  3. Invoke the method showDate() of the object
  4. Invoke the method showAfterDate() of the object

Algorithm for input() method

  1. Create a Scanner object to take input
  2. Take the day number as input and store it in the variable days
  3. Take the year as input and store it in the variable year
  4. Take the number of days after the given date as input and store it in the variable after
  5. Close the Scanner object

Algorithm for postfix(int n) method

  1. Store the last digit of n in the variable r
  2. If r is 1 and n is not 11, return "st"
  3. If r is 2 and n is not 12, return "nd"
  4. If r is 3 and n is not 13, return "rd"
  5. Else return "th"

Algorithm for date_convert(int n, int y) method

  1. Store the number of days in the given year in the variable max
  2. Store 1 in the variable m
  3. Store 0 in the variable d
  4. Store the number of days in each month in the array DAY_COUNT
  5. If the year is a leap year, increment max by 1 and increment the value of DAY_COUNT[1] by 1
  6. Start while loop with n is greater than max*
  7. Subtract max from n
  8. Increment y by 1
  9. End while loop
  10. Start while loop with true
  11. Store the number of days in the current month in the variable m_days
  12. Store the remainder of n divided by m_days + 1 in the variable d
  13. Subtract m_days from n
  14. If n is greater than 0, increment m by 1
  15. Else break the loop
  16. End while loop
  17. Return the string in the format "dth month, year"

Algorithm for showDate() method

  1. Print the string "Date: " and the result of the method date_convert(days, year)

Algorithm for showAfterDate() method

  1. Print the string "Date After after Days: " and the result of the method date_convert(days + after, year), the after is provided to get number of days after a date.

Variable Description

Name Type Description
global
days int Stores the day number
year int Stores the year
after int Stores the number of days after the given date
MONTH_NAME String[] Stores the name of each month
void input()
sc Scanner Used to take input
private String postfix(int n)
r int stores the last digit of n
private String date_convert(int n, int y)
max int Stores the number of days in the given year
m int Stores the month number
d int Stores the day number
DAY_COUNT int[] Stores the number of days in each month
n int Stores the day number provided in the argument
y int Stores the year provided in the argument
m_days int Stores the number of days in the current month
void main()
a NumberToDate Object of the class NumberToDate to invoke its methods