Question

Write a program that prompts the user to enter a date in the format mm/dd/yyyy
where mm is the month , dd is the day and yyyy is a 4 digit year
Check if the date is valid by seeing month is between 1 and 12, day is between 1 to 31 and year is between 1800 to 3000. Also check that if month is 2, day is between 1 to 29
If the date is valid then display the date back in following format dd month year. Use of SimpleDateFormat Java Class is NOT allowed to do this assignment. You need to use String functions from Chapter 4 to do this assignment.

Following is a sample run:
Enter a date in the format mm/dd/yyyy:
02/23/1999
23 Feb 1999

Following is another sample run:

Enter a date in the format mm/dd/yyyy:
02021999
Input String Length should be 10

Following is another sample run:

Enter a date in the format mm/dd/yyyy:
02-23-2000
Invalid Date Format

Following is another sample run:

Enter a date in the format mm/dd/yyyy:
23/02/2000
Invalid Date

Answer 1

import java.util.Scanner;

public class StringDate {
   public static void main(String[] args) {
       String arr[] = { " ", "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep",
               "Oct", "Nov", "Dec" };
       System.out.println("Enter a date in the format ");
       Scanner sc = new Scanner(System.in);
       String date = sc.next();
       //checking if it has invalid length
       if (date.length() < 10) {
           System.out.println("Input String Length should be 10");
           return;
       }
       //splitting the string to get day,month,year
       String splt[] = date.split("/");
       int day = Integer.parseInt(splt[1]);
       int month = Integer.parseInt(splt[0]);
       int year = Integer.parseInt(splt[2]);
       //checking if it valid year and month
       if (year < 1800 || year > 3000 || month < 1 || month > 12) {
           System.out.println("Invalid Date format");
           return;
       }
       if(!(day>=1 && day<getDays(month))){
           System.out.println("Invalid Date format");
           return;
       }
       System.out.println(day+" "+arr[month]+" "+year);

   }
   private static int getDays(int mm) {
       int res = -1;
       switch (mm) {
       case 1:
           res = 31;
           break;
       case 2:
               res = 29;
           break;
       case 3:
           res = 31;
           break;
       case 4:
           res = 30;
           break;
       case 5:
           res = 31;
           break;
       case 6:
           res = 30;
           break;
       case 7:
           res = 31;
           break;
       case 8:
           res = 31;
           break;
       case 9:
           res = 30;
           break;
       case 10:
           res = 31;
           break;
       case 11:
           res = 30;
           break;
       case 12:
           res = 31;
           break;

       }
       return res;
   }
}

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