if (subplot == null) {
            throw new IllegalArgumentException("Null 'subplot' argument.");
        }
        if (weight < 1) {
            throw new IllegalArgumentException("Require weight >= 1.");
        }
        subplot.setParent(this);
        subplot.setWeight(weight);
        subplot.setInsets(new RectangleInsets(0.0, 0.0, 0.0, 0.0));
        subplot.setDomainAxis(null);
        subplot.setOrientation(getOrientation());
        subplot.addChangeListener(this);
        this.subplots.add(subplot);
        this.totalWeight += weight;