require user input to follow string format [closed]

Question

as I am learning java I am also having troubles doing the things I want my program to do. I am watching thenewboston to learn, however, he teach me everything, i.e. how to format user input.

This is my code so far.

import java.util.Scanner;

public class FitnessExtreme {

public static void main(String[] args) {
    // TODO Auto-generated method stub

    System.out.println("Welcome to FitnessExtreme Centre");
    System.out.println("          XX      XX");
    System.out.println("           XX    XX");
    System.out.println("             XXXX");
    System.out.println("           XX    XX");
    System.out.println("          XX      XX");

    int membership = 299;
    double tax = 1.25;
    double total = membership*tax;

    // Scans for user input
    Scanner scan = new Scanner(System.in);

    // Retrieves customer name
    System.out.println("First name: ");
    String fname = scan.next();

    System.out.println("Last name: ");
    String lname = scan.next();

    // Retrieves CPR number
    System.out.println("CPR number: ");
    String cpr = scan.next();

    // Validate CPR format
    if(cpr.length() != 11) {
        System.out.println("Format was not met, please try again");
        System.out.println("CPR number: ");
        cpr = scan.next();
    }

    // Retrieves Telephone number
    System.out.println("Telephone number: ");
    String phone = scan.next();

    // Retrieves Address
    System.out.println("House number: ");
    String hnumber = scan.next();

    System.out.println("Street name: ");
    String sname = scan.next();

    System.out.println("Post code: ");
    String pcode = scan.next();     

    // Customer print out
    System.out.println("Thank you " + fname + " " + lname);
    System.out.println("I have registered following information on you: ");
    System.out.println("CPR number: " + cpr);
    System.out.println("Telephone number: " + phone);
    System.out.println("House number: " + hnumber);
    System.out.println("Street name: " + sname);
    System.out.println("Post code " + pcode);       

    // Continue?
    System.out.println("");
    System.out.println("If this information is correct and you want to continue, please enter 'yes'");
    String verify = scan.next();

    if(verify.equals("yes")) {
        System.out.println("Alright " + fname + " your price is gonna be:");
        System.out.println("Membership subscription - subtotal: " + membership);
        System.out.println("VAT " + tax);
        System.out.println("Total: " + total);
    }
  }
}

So i need to format the user input "cpr", i need to to be in a ######-#### format. I got the length part, however, if the user doesn't fulfill the requirement regarding the format, I want it to say please try again, like I did with cpr. I found multiple guides on the format on Google but I couldn't find one that does the formatting the way I want it.

Who better to ask than you guys! Also if you have tips on how i can improve my program please share.

Answer 1

To a beginner, I would suggest not the "shortest" solution, but one that is easy to understand.

You say you want this format ######-####; in other words: 6 digits, dash, 4 digits.

You can build a check for that like this:

1. You check that length is 11 --- fine you already got that
2. You iterate your input string; and you check that each character is a digit. [ except for the 7th character - that must be a "-" ! ]

To check if a char is a digit, you can use Character.isDigit().

When that works, you can pull that checking into a single regular expression; and experiment with that.

But as said; a beginner should start by doing such things manually. Understand what is going on; and only then; move on and look into more powerful, but also more complex solutions.