Java regular expression characters in a string

Question

Im working on a project now that has the user enter an RFID which must be a string fixed at 9 characters long and represented in hexadecimal, so each character is either a digit from 0 to 9 or one of the letters A through F. (case insensitive)

Then I also need to take an input of the shelf position which is fixed at 6 characters, the first character is 's' to designate that it is a shelf position and it is followed by a 5 digit number. EX: "s04013" (case insensitive)

Im using a scanner to store the inputs in the variable RFID and originalLocation. I have two questions:

1)How can I check and make sure the input is valid so I can throw an exception if is not? I think I have to use regular expressions but I'm not sure.

2)Is there a way to fix a string's length to a specified amount of characters?

Any help/advice would be greatly appreciated Thank you so much!

Answer 1

(s[0-9]{5}|[0-9a-f]{9})

This regular expression should solve your problem.

See DEMO here

String str = "s04013"; 
String regex = "(s[0-9]{5}|[0-9a-f]{9})";
if(str.matches(regex)) {
  /*Do something*/
} else {
   throw new Exception("Token does not matach");
}

Answer 2

I dont know if I understand your question correctly but this is what i came up with what i gathered from your question. Code:

import java.util.Scanner;

public class RegexTry {
    public static void main(String args[]){

    Scanner scanner = new Scanner(System.in);
    String RFIDreg = "^[0-9A-Fa-f]{9}$";
    String Shelfreg = "^s[0-9]{5}$";

    System.out.print("Enter RFID: ");
    String RFIDString = scanner.nextLine();//input RFID string

    /*Check for RFID string*/
    if(RFIDString.matches(RFIDreg)){
        System.out.println("Correct");
    }
    else{
        System.out.println("False");
    }
    /*Check for RFID string*/

System.out.print("Enter Shelf Position: ");
String Shelfstring = scanner.nextLine();//input Shelf string

    /*Check for Shelf string*/
    if(Shelfstring.matches(Shelfreg)){
        System.out.println("Correct");
    }
    else{
        System.out.println("False");
    }
    /*Check for Shelf string*/
}

}