Advice, writing a social security code

问题

Im new to java and my class we need to write a program where the user inputs there social security code in the form of XXXXXXXXX and it returns it in the form of XXXX-XX-XXX. For example if there code was 123456789 it would be returned to them as 123-45-6789.

Here is what I have, I would like to use substrings to finish it off.

import java.util.Scanner;

public class HWSocialSecuritySh  {
public static void main (String [] args) {
    Scanner reader = new Scanner (System.in);

    String name;
    int ssn;
    System.out.print ("Enter nine digit social security number without dashes: ");
    ssn= reader.nextInt();
    System.out.print("Your formatted social security number is: ");
    System.out.println(snn.substring(,) );

   }
   }

This is the new code

import java.util.Scanner;

public class HWSocialSecuritySH  {
public static void main (String [] args) {
    Scanner reader = new Scanner (System.in);

    String name;
    String Ssn="ssn";

    System.out.print ("Enter nine digit social security number without dashes: ");
    Ssn= reader.nextLine();
    System.out.print("Your formatted social security number is: ");
    System.out.println (Snn.substring(0,3) +"-"snn.substring(4,6) + "-"snn.substring(7,9);

}
}

回答1:

Actually a more appropriate way to do this would be to use a Matcher with a Pattern representing a regex containing the subgroups of the social security number as capturing groups:

final Pattern ssnFormat = Pattern.compile("^(\\d{3})(\\d{2})(\\d{4})$");

Matcher m = ssnFormat.matcher(ssn);  // make ssn a string!

if (m.find()) {
    System.out.printf("%s-%s-%s%n", m.group(1), m.group(2), m.group(3));
} else {
    System.err.println("Enter a valid social security number!");
}

As noted, a social security number, while representable as an integer, is really a string of digits: it's meaningless as a number. Therefore, you should store it as a String and not as an int.

Now, in your new code, you're almost there, but still have a few issues:

It's String, not string.
Now that ssn is a string, you can't assign it to the result of reader.nextInt(), since that returns an int. Instead, you'll want to use reader.nextLine().
The ranges of the second and third substring() calls are slightly off. Refer to the method's documentation.

来源：https://stackoverflow.com/questions/19128108/advice-writing-a-social-security-code

标签

java

substring

reformat