/* 12/4/2019
 * Character class
 * validate product number
 * 2 upper characters followed by 2 digits
 * ex: AB00, GH98
 * not good: qW77, ABCD, 1234 etc
 */
import java.util.Scanner;

public class ProductNum {
  
  public static void main(String[] args) {
    
    Scanner sc = new Scanner(System.in);
    System.out.print("Enter a product#"); 
    String prodNum = sc.next();
    ch = prodNum.charAt(0);
    // alternative way:
    // if (ch >= 'A' && ch <= 'Z')
    if (Character.isUpperCase(prodNum.charAt(0))
          && Character.isUpperCase(prodNum.charAt(1))
          && Character.isDigit(prodNum.charAt(2))
          && Character.isDigit(prodNum.charAt(3)))
      System.out.println(prodNum + " is valid.");
    else
      System.out.println(prodNum + " is not valid");
  }
}