I want to print an error message if a letter comes after the first two letters in the following expression.

EN545454545

CodePudding user response：

You can try using the tryParse method of num, if it fails parsing it returns null which means it contained some illegal characters

  String code = 'EN545454545';
  if (num.tryParse(code.substring(2)) == null) {
    // Handle error
  }