Making A Password Validator And One Of Rules Is: The Key Must Contain Either A '#' or A '_', But NOT Both

I am making a Password/Key Validator with a set of rules which must be met to validate the Password/Key.

These rules are the following: - The key be at least 7 characters long, AND at most 20 characters long, AND - The key must not start with the special characters '#' or '', AND - The key must not have a space character anywhere, AND - The key must have at least one Upper case character and at least one Lower case character, AND - The key must not contain the user's name, AND - The key must contain either a '#' or a '', but not both.

I have managed to get all to work except for the last rule "The key must contain either a '#' or a '_', but not both."

The code I currently have is below. I am new to learning java so please understand.

 * Asks user for key word and the name and then checks if it is a valid key word.
 */
public void doCompletion(){
    String key = UI.askString("Key:   ");
    String name = UI.askString("Your name:   ");
    this.validateKeyCompletion(key, name);
}

/** COMPLETION
 * Report that the key is valid or report ALL the rules that the key failed.
 */
public void validateKeyCompletion(String key, String name){
    /*# YOUR CODE HERE */
   int characterNumber = key.length();
   boolean hasUppercase;
   boolean hasLowercase;
   hasUppercase = !key.equals(key.toLowerCase());
   hasLowercase = !key.equals(key.toUpperCase());
   String specialChars = "(.*[ #  _  ].*)";
   if (characterNumber < 7 || characterNumber > 20){
    UI.println("Invalid: Key length must not be less than 7 or greater than 20");
   }
   else if (key.startsWith ("#") || (key.startsWith ("_"))){
    UI.println("Invalid: Key cannot start with '#' or '_'");
   } 
   else if (key.contains(" ")){
    UI.println("Invalid: Key cannot contain ' '");
   }
   else if(!hasUppercase)
   {
    UI.println("Invalid: Key must contain an uppercase character");
   }
   else if(!hasLowercase)
   {
    UI.println("Invalid: Key must contain a lowercase character");
   }
   else if(key.matches(name)){
    UI.println("Invalid: Key cannot contain Username");
   }
   else if(!key.matches(specialChars)){
    UI.println("Invalid: Key must contain either a '#' or a '_', but not both");
   } 
   else {
    UI.println("Valid");
   }


}