@Override
    public String getArrowString(){
        String arrows = "-";
        String arrowStart = startArrow.getArrowStyle();
        String arrowEnd = endArrow.getArrowStyle();
        if(!arrowStart.equals(ArrowHead.DEFAULT_ARROW) &&
           !arrowEnd.equals(ArrowHead.DEFAULT_ARROW)){
            arrows = arrowStart+"-"+arrowEnd;
        }else if(!arrowStart.equals(ArrowHead.DEFAULT_ARROW) ||
           !arrowEnd.equals(ArrowHead.DEFAULT_ARROW)){
            arrows = arrowStart+arrowEnd;
        }
        return arrows;
    }