code: public boolean barIsEmpty(Bar bar) {
          for (Object o : getBarContent(bar)) {
              MusicElement me = (MusicElement) o;
              if (!(me instanceof BarLine) && !(me instanceof Spacer))
                  return false;
          }
  		return true;
  	}
docs: Return true if the bar is empty or contains only barline and spacer(s).
  False if barline contain other kind of music element