Question

I need to validate a user’s screen name to make sure that it can not have more than one hyphen or underscore I don’t want people’s screen names to be all punctuation.

This is the validation I have so far:

public boolean validateScreenName(String screenName) {
  // Check screen name has > 0 chars and that it contains only a-z, A-Z, _ and -
  boolean validated = false;

  if (screenName.matches("[a-zA-Z0-9_-]{1,20}") 
      && (! screenName.equals("")) 
      && (! screenName.contains("\\s"))) {
    validated = true; 
  } else {
    validated = false;
  }
  return validated;
}

I want to add the no-multiple-hyphen/underscore validation as another if condition maybe in the form of a RegEx?

Answer 1

You could use:

screenName.matches("^(?=[^_-]*[_-]?[^_-]*$)[a-zA-Z0-9_-]{1,20}$")

The other conditions are not needed, they are redundant.