public Object clone() throws CloneNotSupportedException {
        AbstractCategoryItemLabelGenerator clone 
            = (AbstractCategoryItemLabelGenerator) super.clone();
        if (this.numberFormat != null) {
            clone.numberFormat = (NumberFormat) this.numberFormat.clone();
        } 
        if (this.dateFormat != null) {
            clone.dateFormat = (DateFormat) this.dateFormat.clone();
        } 
        return clone;