public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof XYSeries)) {
            return false;
        }
        if (!super.equals(obj)) {
            return false;
        }
        XYSeries that = (XYSeries) obj;
        if (this.maximumItemCount != that.maximumItemCount) {
            return false;
        }
        if (this.autoSort != that.autoSort) {
            return false;
        }
        if (this.allowDuplicateXValues != that.allowDuplicateXValues) {
            return false;
        }
        if (!ObjectUtilities.equal(this.data, that.data)) {
            return false;
        }
        return true;
    }

    /**
     * Returns a hash code.
     *
     * @return A hash code.
     */
    public int hashCode() {
        int result = super.hashCode();
        // it is too slow to look at every data item, so let's just look at
        // the first, middle and last items...
        int count = getItemCount();
        if (count > 0) {
            XYDataItem item = getDataItem(0);
            result = 29 * result + item.hashCode();
        }
        if (count > 1) {
            XYDataItem item = getDataItem(count - 1);
            result = 29 * result + item.hashCode();
        }
        if (count > 2) {
            XYDataItem item = getDataItem(count / 2);
            result = 29 * result + item.hashCode();
        }
        result = 29 * result + this.maximumItemCount;
        result = 29 * result + (this.autoSort ? 1 : 0);
        result = 29 * result + (this.allowDuplicateXValues ? 1 : 0);
        return result;