Question

Coding in Java

• private int getLastDayOfMonth(int m, int y)– return the last day of the month and year entered as input parameter. Remember to invoke the isLeapYear method when appropriate. If the month entered as input parameter is 2 (February) and the year passed as input parameter is a leap year this method should return 29.

• private boolean isDateValid (int m, int d, int y) – return true if day, month, and year entered as input parameters form a valid date, return false otherwise. To be able to write the logic for this method you need to know the number of days for each month of the year, whether a year is a leap year (leap years have 29 days for the month of February, not leap years have 28 days for the month of February). Remember to invoke the isLeapYear and getLastDayOfMonth methods when appropriate. Valid months are between 1 and 12 (inclusive) and consider a positive number as a valid year.

Examples:

• Invalid dates:
  • 2/29/2019 – 2019 is not a leap year, the number of days in February is 28
  • 13/17/2019 – 13 is not a valid month
  • 11/31/2019 – the month of November only has 30 days
  • 6/23/-2019 – the year cannot be negative
• Valid dates:
  • 2/29/2020 – 2020 is a leap year, February has 29 days
  • 11/30/2019 – nothing wrong, November has 30 days
  • 6/22/1992 – nothing wrong here.

Answer 1

I have implemented these method under a single class Test , so in order to use them(for getting output) i have made them static and used them under our main method.

Since there is no information about input, I have asked user input to enter day, month ,year separately and then perform the tasks.(Please see output screenshots to get clarity).

Please go through the code, test run it for various inputs, Open for suggestions, Thanks!

import java.util.Scanner; //to prompt for user input

public class Test {

   public static void main(String[] args) {
       Scanner sc = new Scanner(System.in);// to prompt user input
       System.out.print("Enter month: ");
       int month = sc.nextInt();// stores month
       System.out.print("Enter day: ");
       int day = sc.nextInt();// stores day
       System.out.print("Enter year:");
       int year = sc.nextInt();// stores year
       /*
       * method call isDateValid(m,d,y) to check if the date entered is valid or not
       */
       if (isDateValid(month, day, year)) {
           System.out.println(month + "/" + day + "/" + year + " Valid Date");// prints if the date is valid
       } else {
           System.out.println(month + "/" + day + "/" + year + " Invalid Date");// prints if the date is invalid
       }
       sc.close();
   }
   /*month, day, year are passed as argument to below function to test whether it forms a valid date or not*/
   private static boolean isDateValid(int month, int day, int year) {
       boolean isDateValid = false;//boolean to validate the date
       int lastDayOfMonth = getLastDayOfMonth(month, year);/*stores the last day of the month(passed as arg)*/
       /*checks if month, day, year are positive values*/
       if (month > 0 && day > 0 && year > 0) {
           /*if month entered is invalid getLastDayOfMonth returns 0(look for method implementation)*/
           if (lastDayOfMonth == 0) {
               /*returns false here since isValidDate was initialized as false*/
               return isDateValid;
           }
           /*if its a valid month then check for entered day as valid or not should be between 1 and lastDayOfMonth*/
           if (day >= 1 && day <= lastDayOfMonth) {
               isDateValid = true;
               return isDateValid;//returns true here since date is found valid
           }
       }
       return isDateValid;//returns false here for negative values of either of day, month, year
   }
   /*returns the last day of month and year passed as argument*/
   private static int getLastDayOfMonth(int month, int year) {
       /*if month is valid i.e between 1 and 12*/
       if ((month >= 1 && month <= 12)) {
           /*For months January,March,May,July,August,October,December last day is 31st*/
           if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12) {
               return 31;
           }
           /*For months September,April,June,November last day is 30th*/
           else if (month == 9 || month == 4 || month == 6 || month == 11) {
               return 30;
           }
           /*For month February we need to check if its a leap year or not*/
           else {
               /*checks for year being a leap year or not and return 29 or 28 accordingly*/
               if (isLeapYear(year)) {
                   return 29;
               }
               return 28;
           }
       }
       /*returns 0 for invalid month entered*/
       return 0;
   }
   /*returns true if its a leap year and false if not*/
   private static boolean isLeapYear(int year) {
       /*a leap year should be either be divisible by 400 or divisible by 4 and not divisible by 100*/
       if (((year % 4 == 0) && (year % 100 != 0)) || (year % 400 == 0)) {
           return true;//returns true for a leap year
       }
       return false;//returns false if not leap year
   }

}

screenshot of the code:

output when you run above code(multiple runs):

to format your code Ctrl+a then Ctrl+Shift+f(for eclipse IDE)