[Java][Exercise] String countYZ code practice

Given a string, count the number of words ending in 'y' or 'z' -- so the 'y' in "heavy" and the 'z' in "fez" count, but not the 'y' in "yellow" (not case sensitive). We'll say that a y or z is at the end of a word if there is not an alphabetic letter immediately following it. (Note: Character.isLetter(char) tests if a char is an alphabetic letter.)

Expected result

Code

public int countYZ(String str) {
      int amount = 0;
      String[] parts =str.split("\\P{Alpha}+");
        for (String part : parts) {
            if(part.length()>0){
                char lastChar = Character.toLowerCase(part.charAt(part.length()-1));
                if(lastChar=='y' || lastChar=='z'){
                    amount++;
                }
            }
        }
      return amount;
}

Reference
http://codingbat.com