1  import java.util.Scanner;
  2  
  3  public class HexDigit2Dec {
  4    public static void main(String[] args) {
  5      Scanner input = new Scanner(System.in);
  6      System.out.print("Enter a hex digit: ");
  7      String hexString = input.nextLine();
  8      
  9      // Check if the hex string has exactly one character
 10      if (hexString.length() != 1) {
 11        System.out.println("You must enter exactly one character");
 12        System.exit(1);
 13      }
 14      
 15      // Display decimal value for the hex digit
 16      char ch = Character.toUpperCase(hexString.charAt(0));    
 17      if ('A' <= ch && ch <= 'F') {
 18        int value = ch - 'A' + 10;
 19        System.out.println("The decimal value for hex digit "
 20          + ch + " is " + value);
 21      }
 22      else if (Character.isDigit(ch)) {
 23        System.out.println("The decimal value for hex digit "
 24          + ch + " is " + ch);
 25      }
 26      else {
 27        System.out.println(ch + " is an invalid input");
 28      }
 29    }
 30  }
            

Output