Solution to Challenge "Applying a Discount Code"

// You check if the char is not a letter OR not the $ symbol, you should be checking if it is not a letter AND not the $ symbol.

// In other words change the || (OR) operator to && (AND) in your if statement like this:

private String normalizeDiscountCode(String discountCode){
  for(char c : discountCode.toCharArray()){
    if(!Character.isLetter(c) && c != '$'){
      throw new IllegalArgumentException("Invalid discount code");
    }
  }
  return discountCode.toUpperCase();
}

// And you will be able to pass the challenge.