Stuck in while loop when trying to validate a string input

Question

So I am trying to take an input for date of birth in the from of DD/MM/YYYY the input cannot exceed 10 characters in length and I must make sure it is in the proper format to avoid the user inputting something like A51/1/1982, I think I have it written correctly at least to my knowledge :) but I am now forever stuck in the while loop when checking the input

       System.out.println("Please enter your date of birth in the format DD/MM/YYYY");
   dateOfBirth = scanner.nextLine(); //Read date of birth
   dob0 = dateOfBirth.substring(0);// to check char 0 is between 0-3
   dob1 = dateOfBirth.substring(1);// to check char 1 is between 0-9
   dob2 = dateOfBirth.substring(2);// to check char 2 is between /
   dob3 = dateOfBirth.substring(3);// to check char 3 is between 0-1
   dob4 = dateOfBirth.substring(4);// to check char 4 is between 0-9
   dob5 = dateOfBirth.substring(5);// to check char 5 is between /
   dob6 = dateOfBirth.substring(6);// to check char 6 is between 1-2
   dob7 = dateOfBirth.substring(7);// to check char 7 is between 0-9
   dob8 = dateOfBirth.substring(8);// to check char 8 is between 0-9
   dob9 = dateOfBirth.substring(9);// to check char 9 is between 0-9
   dob = dateOfBirth.length(); //convert string to int to check length
   while (dob !=10 || !dob0.matches("[0-3]+") || !dob1.matches("[0-9]+") ||      !dob2.matches("[/]+")
    || !dob3.matches("[0-1]+") || !dob4.matches("[0-9]+") || !dob5.matches("[/]+")
    || !dob6.matches("[1-2]+") || !dob7.matches("[0-9]+") || !dob8.matches("[0-9]+") 
    || !dob9.matches("[0-9]+"))//check all values
   {
   System.out.println("Please make sure you enter your date of birth in the format DD/MM/YYYY");
   dateOfBirth = scanner.nextLine();
   }

I am guessing I have probably gone the long away around this bue any help would be appreciated :)

Thanks

Wouter · Accepted Answer · 2013-10-26 12:42:03Z

1

You are not reevaluating the new user input. Only the first line entered. The whole dob0= .. dob = stuff should go inside the while loop after the new input has been entered as well.

answered Oct 26, 2013 at 12:42

Wouter

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1 Comment

Chris Over a year ago

Thank you it is nice to see where I was going wrong with it :)

tobias_k · Accepted Answer · 2013-10-26 13:02:34Z

0

The problem is that your while condition tests the several dobX variables, but you do not update those variables inside the loop. But that's only part of the problem. Instead of exracting the individual characters and testing each character with another regular expression, you should just use one regular expression for testing the whole string.

while (! dateOfBirth.matches("[0-3][0-9]/[0-1][0-9]/[1-2][0-9]{3}") { 
    dateOfBirth = scanner.nextLine();
}

Or even better, use a class like SimpleDateFormat to try to parse the string to a date.

new SimpleDateFormat("dd/MM/yyyy").parse("26/10/2013");

Just put a try/catch block inside your while loop. If the parse succeds, break from the loop, if you catch an exception, print the message to the user and repeat.

edited Oct 26, 2013 at 13:02

answered Oct 26, 2013 at 12:43

tobias_k

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1 Comment

Chris Over a year ago

Thank you very much I knew I was overdoing it trying to figure it out :) I went with the while (!dateofbirth.matches statement simply because we have not covered SimpleDateFormat in my course yet :) Once again thanks :)

Senthilkumar Gopal · Accepted Answer · 2013-10-26 13:12:02Z

0

a simple means will be to use SimpleDateFormat and use the parse() function. If there is a ParseException, it means that the input is not in the correct format.

http://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html#parse(java.lang.String, java.text.ParsePosition)

answered Oct 26, 2013 at 13:12

Senthilkumar Gopal

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3 Comments

Senthilkumar Gopal Over a year ago

Also, this can help you validate number of days in feb not exceeding 30 and other date based validations

Chris Over a year ago

Thank you I did not use this because we have not covered it yet in our course and the code is for a project and I did not want to add in what we have not done yet,but it is good to know for the future and thank you for the link has a lot of useful info there :)

Senthilkumar Gopal Over a year ago

Nice to know. Please accept the answer if you feel this will help others as well. Good luck!

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