code: public static boolean isAllAlpha(String str) {
  
  	if (str == null) return false;
  
  	for (int i = str.length() - 1; i >= 0; i--) {
  
  	    if (!Character.isLetter(str.charAt(i))) return false;
  	}
  
  	return true;
      }
docs: returns true if all characters in the string are letters
  
  @param str
  @return