Question

This is dealing with java to start.
My goal is to take in a Vin number and store it into a string. Make sure it has no more than 9 characters. Also the Vin Number is only supposed to contain numbers and letters a-z or A-Z. If the user inputs an invalid Vin number it should loop back around and prompt for a new Vin Number. My problem is telling whether the string contains anything other than integers or letters. I’ve seen the Utility.IsAlphaNumeric method but I can’t figure out how to implement it or whether it’s even a java method. NetBeans gives me errors whenever I try to use it.

private static String checkVin() {
    Scanner input = new Scanner(System.in);
    String vinNumber = "";
    do {
        System.out.println("Please enter the vin number of the car");
        vinNumber = input.next();
        if (vinNumber.length() > 9) {
            System.out.println("invalid input for Vin number");
        }
        for (int i = 0; i < vinNumber.length(); i++) {
            char currentCharacter = vinNumber.charAt(i);

            if ((currentCharacter < '0' || currentCharacter > '9')
                    || !( currentCharacter < 'a' || currentCharacter > 'z')
                    || !(currentCharacter > 'A' || currentCharacter > 'Z'));
            System.out.println("invalid input for Vin Number");
            break;
        }
        return vinNumber;

    } while (true);
}

Answer 1

Utility is not the name of a class from the core libraries.

You can replace the entire check loop with

import java.util.regex.Pattern;
import java.util.regex.Matcher;

private static final Pattern VALID_VIN_NUMBER = Pattern.compile(
    "[0-9a-zA-Z]{1,9}");

public static boolean isVin(String s) {
  return VALID_VIN_NUMBER.matcher(s).matches();
}