code: public static boolean isStop(String str) {
  		if (str.compareTo(".") == 0) {
  		    return true;
  		}
  	
  		if (str.compareTo("?") == 0) {
  		    return true;
  		}
  		
  		if (str.compareTo("!") == 0) {
  		    return true;
  		}
  		
  		return false;
      }
docs: Checks if is stop.
  
  @param str string
  @return true, if the input is the stop character '.'