Write a method called validateDate that takes a single String argument and check

Question

Write a method called validateDate that takes a single String argument and checks whether this String is a valid date in the form mm/dd/yyyy. Your method should throw an InvalidDateException if the date is not valid.

• There could be dierent cases which makes the date invalid, make sure to account for all the cases. Assume all months have 31 days.

• To extract month, day and year components from the single String parameter, you can use the following method of the String class substring(b, e): extracts and returns the substring from position b through position e-1. Generates an IndexOutOfBoundsException if b or e-1 is illegal.

• Recall also that Integer.parseInt(...) can be used to convert a String to an int, and this method can possibly throw a NumberFormatException.

• Do NOT catch InvalidDateException inside the method.

Explanation / Answer

DateFormatChecker.java

import java.util.Scanner;

public class DateFormatChecker {

   /**
   * @param args
   */
   public static void main(String[] args) {
       // TODO Auto-generated method stub
       try{
       Scanner scan = new Scanner(System.in);
       System.out.println("Please enter the date in the format (mm/dd/yyyy)");
       String date = scan.next();
       validateDate(date);
       }
       catch(InvalidDateException e){
           System.out.println(e);
       }
   }
   public static void validateDate(String date) throws InvalidDateException{
       int month = Integer.parseInt(date.substring(0, 2));
       int day = Integer.parseInt(date.substring(3, 5));
       int year = Integer.parseInt(date.substring(6));
       if(month < 1 || month > 12){
           throw new InvalidDateException("Invalid Month in Given Date");
       }
       if(date.substring(6).length() != 4 ){
           throw new InvalidDateException("Invalid year in Given Date. Year should be a four digit number");
       }
       if((month ==1 || month == 3 || month ==5 || month == 7 || month ==8 || month == 10 || month == 12) && (day < 1 || day > 31) ){
           throw new InvalidDateException("Invalid day in Given Date. We have 31 days in that particulat month starts from 1 to 31");
       }
       else if((month == 4 || month == 6 || month == 9 || month ==11) && (day < 1 || day > 30)){
           throw new InvalidDateException("Invalid day in Given Date. We have 30 days in that particulat month starts from 1 to 30");
       }
       else if(month == 2 && (day < 1 || day > 28) && year % 4 != 0){
           throw new InvalidDateException("Invalid day in Given Date. We have 28 days in that particulat month starts from 1 to 28");
       }
       else if(month == 2 && (day < 1 || day > 29) && year % 4 == 0){
           throw new InvalidDateException("Invalid day in Given Date. We have 29 days in that particulat month starts from 1 to 29");
       }
   }

}

InvalidDateException.java

public class InvalidDateException extends Exception{
   String str1;
   public InvalidDateException(){
      
   }
  
   public InvalidDateException (String s){
       this.str1 = s;
   }

public String toString(){
return (str1) ;
}  
}

Output:

Please enter the date in the format (mm/dd/yyyy)
13/12/2011
Invalid Month in Given Date

Please enter the date in the format (mm/dd/yyyy)
12/12/201
Invalid year in Given Date. Year should be a four digit number

Please enter the date in the format (mm/dd/yyyy)
11/31/2011
Invalid day in Given Date. We have 30 days in that particulat month starts from 1 to 30

Please enter the date in the format (mm/dd/yyyy)
02/30/2016
Invalid day in Given Date. We have 29 days in that particulat month starts from 1 to 29

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