Searching a string for a non-letter character in a loop

Question

So let's imagine we have this loop that obtains input from the user in the form of strings. With that input, what we want to do is set up a set of validations that will check if certain criteria are met. If all of these conditions are met, it'll complete the action in question. However; if it doesn't, it'll tell them the error and restart the process.

My question is about validating the existance (or non-existance) of a letter in a string. I have this program and for one of these validations, I need to check the entire string. If the string does not have at least one character that isn't a letter, I want to halt the action and explain that a non-letter character is required.

The problem is that I am not sure how I could replicate this in an expression in an if loop. Here's what I have so far.

public static changePassword() // Method that runs through the process of changing the password. 
 {
      // Retrieving the current and new password from the user input.
      System.out.println("Welcome to the change password screen.");
      Scanner keyboard = new Scanner(System.in);
      System.out.print("Please enter your current password: ");
      String currentPassword = keyboard.nextLine();
      System.out.print("Please enter the new password: ");
      String newPassword1 = keyboard.nextLine();
      System.out.print("Please enter the new password again: ");
      String newPassword2 = keyboard.nextLine();

      // Validating the new password entry.
      if (newPassword1.equals(newPassword2)) // Checking to see if the new password was entered exactly the same twice.
      {
        if (newPassword1.length() >= 6) // Checking to see if the new password has 6 or more characters.
        {
           if (**some expression**) // Checking to see if the password has at least one non-letter character.
           {
              currentPassword = newPassword1 // If all conditions are met, it sets the current password to the password entered by the user.
           }
           else // If there isn't a non-letter character, it informs the user and restarts the process.
           {
              System.out.println("The new password must have a non-letter character.");
              changePassword();
           }
        }
        else // If there is less than 6 characters, it informs the user and restarts the process.
        {
           System.out.println("The new password can not be less than 6 characters.");
           changePassword();
        }
      }
      else // If the new passwords don't match, it informs the user and restarts the process.
      {
        System.outprintln("The passwords must match.");
        changePassword();
      }


 }

you could use of `regex` try this [link](http://stackoverflow.com/questions/9587907/how-to-check-if-string-has-at-least-one-letter-number-and-special-character-in) — Ker p pag, Sep 01 '14 at 02:18

score 0 · Accepted Answer · answered Sep 01 '14 at 02:22

Assuming by "letter" you mean an english character in A-Z, a-z, just iterate through the string and return true if you encounter a character whose int value is outside the letter range.

public static boolean containsNonLetter(String s){
    for(int i = 0; i < s.length(); i++){
        int ind = (int)s.charAt(i);
        if(ind < 65 || (ind > 90 && ind < 97) || ind > 122)
            return true;
    }
    return false;
}

score 0 · Answer 2 · answered Sep 14 '14 at 02:27

I am making the assumption that by letter you meant alphabets. If you use regex pattern you can have a very clean code as well you have ability to update the pattern as necessary. To learn more check Java Pattern. Here is the code.

private static final Pattern APLHA = Pattern.compile("\\p{Alpha}");

public static boolean hasLetter(String input) {

    return APLHA.matcher(input).find();
}

Searching a string for a non-letter character in a loop

2 Answers2