}

    /**
     * Sets the categories for the dataset.
     *
     * @param categoryKeys  an array of objects representing the categories in 
     *                      the dataset.
     */
    public void setCategoryKeys(Comparable[] categoryKeys) {

        // check arguments...
        if (categoryKeys == null) {
            throw new IllegalArgumentException("Null 'categoryKeys' argument.");
        }

        if (categoryKeys.length != this.startData[0].length) {
            throw new IllegalArgumentException(
                "The number of categories does not match the data."
            );
        }

        for (int i = 0; i < categoryKeys.length; i++) {
            if (categoryKeys[i] == null) {
                throw new IllegalArgumentException(
                    "DefaultIntervalCategoryDataset.setCategoryKeys(): "
                    + "null category not permitted.");
            }
        }

        // make the change...
        this.categoryKeys = categoryKeys;
        fireDatasetChanged();

    }

    /**
     * Returns the data value for one category in a series.
     * <P>
     * This method is part of the CategoryDataset interface.  Not particularly
     * meaningful for this class...returns the end value.
     * @param series    The required series (zero based index).
     * @param category  The required category.
     * @return The data value for one category in a series (null possible).
     */
    public Number getValue(Comparable series, Comparable category) {
        int seriesIndex = getSeriesIndex(series);
        int itemIndex = getColumnIndex(category);
        return getValue(seriesIndex, itemIndex);
    }

    /**
     * Returns the data value for one category in a series.
     * <P>
     * This method is part of the CategoryDataset interface.  Not particularly
     * meaningful for this class...returns the end value.
     *
     * @param series  the required series (zero based index).
     * @param category  the required category.
     *
     * @return The data value for one category in a series (null possible).
     */
    public Number getValue(int series, int category) {
        return getEndValue(series, category);
    }

    /**
     * Returns the start data value for one category in a series.
     *
     * @param series  the required series.
     * @param category  the required category.
     *
     * @return The start data value for one category in a series 
     *         (possibly <code>null</code>).
     */
    public Number getStartValue(Comparable series, Comparable category) {
        int seriesIndex = getSeriesIndex(series);
        int itemIndex = getColumnIndex(category);
        return getStartValue(seriesIndex, itemIndex);
    }

    /**
     * Returns the start data value for one category in a series.
     *
     * @param series  the required series (zero based index).
     * @param category  the required category.
     *
     * @return The start data value for one category in a series 
     *         (possibly <code>null</code>).
     */
    public Number getStartValue(int series, int category) {

        // check arguments...
        if ((series < 0) || (series >= getSeriesCount())) {
            throw new IllegalArgumentException(
                "DefaultIntervalCategoryDataset.getValue(): "
                + "series index out of range.");
        }

        if ((category < 0) || (category >= getCategoryCount())) {
            throw new IllegalArgumentException(
                "DefaultIntervalCategoryDataset.getValue(): "
                + "category index out of range.");
        }

        // fetch the value...
        return this.startData[series][category];

    }

    /**
     * Returns the end data value for one category in a series.
     *
     * @param series  the required series.
     * @param category  the required category.
     *
     * @return The end data value for one category in a series (null possible).
     */
    public Number getEndValue(Comparable series, Comparable category) {
        int seriesIndex = getSeriesIndex(series);
        int itemIndex = getColumnIndex(category);
        return getEndValue(seriesIndex, itemIndex);
    }

    /**
     * Returns the end data value for one category in a series.
     *
     * @param series  the required series (zero based index).
     * @param category  the required category.
     *
     * @return The end data value for one category in a series (null possible).
     */
    public Number getEndValue(int series, int category) {

        // check arguments...
        if ((series < 0) || (series >= getSeriesCount())) {
            throw new IllegalArgumentException(
                "DefaultIntervalCategoryDataset.getValue(): "
                + "series index out of range.");
        }

        if ((category < 0) || (category >= getCategoryCount())) {
            throw new IllegalArgumentException(
                "DefaultIntervalCategoryDataset.getValue(): "
                + "category index out of range.");
        }

        // fetch the value...
        return this.endData[series][category];

    }

    /**
     * Sets the start data value for one category in a series.
     * 
     * @param series  the series (zero-based index).
     * @param category  the category.
     * 
     * @param value The value.
     */
    public void setStartValue(int series, Comparable category, Number value) {

        // does the series exist?
        if ((series < 0) || (series > getSeriesCount())) {
            throw new IllegalArgumentException(
                "DefaultIntervalCategoryDataset.setValue: "
                + "series outside valid range.");
        }

        // is the category valid?
        int categoryIndex = getCategoryIndex(category);
        if (categoryIndex < 0) {
            throw new IllegalArgumentException(
                "DefaultIntervalCategoryDataset.setValue: "
                + "unrecognised category.");
        }

        // update the data...
        this.startData[series][categoryIndex] = value;
        fireDatasetChanged();

    }

    /**
     * Sets the end data value for one category in a series.
     *
     * @param series  the series (zero-based index).
     * @param category  the category.
     *
     * @param value the value.
     */
    public void setEndValue(int series, Comparable category, Number value) {

        // does the series exist?
        if ((series < 0) || (series > getSeriesCount())) {
            throw new IllegalArgumentException(
                "DefaultIntervalCategoryDataset.setValue: "
                + "series outside valid range.");
        }

        // is the category valid?
        int categoryIndex = getCategoryIndex(category);
        if (categoryIndex < 0) {
            throw new IllegalArgumentException(
                "DefaultIntervalCategoryDataset.setValue: "
                + "unrecognised category.");
        }

        // update the data...
        this.endData[series][categoryIndex] = value;
        fireDatasetChanged();

    }

    /**
     * Returns the index for the given category.
     *
     * @param category  the category.
     *
     * @return The index.
     */
    private int getCategoryIndex(Comparable category) {
        int result = -1;
        for (int i = 0; i < this.categoryKeys.length; i++) {
            if (category.equals(this.categoryKeys[i])) {
                result = i;
                break;
            }
        }
        return result;
    }

    /**
     * Generates an array of keys, by appending a space plus an integer
     * (starting with 1) to the supplied prefix string.
     *
     * @param count  the number of keys required.
     * @param prefix  the name prefix.
     *
     * @return An array of <i>prefixN</i> with N = { 1 .. count}.
     */
    private Comparable[] generateKeys(int count, String prefix) {
        Comparable[] result = new Comparable[count];
        String name;
        for (int i = 0; i < count; i++) {
            name = prefix + (i + 1);
            result[i] = name;
        }
        return result;
    }

    /**
     * Returns a column key.
     *
     * @param column  the column index.
     *
     * @return The column key.
     */
    public Comparable getColumnKey(int column) {
        return this.categoryKeys[column];
    }

    /**
     * Returns a column index.
     *
     * @param columnKey  the column key.
     *
     * @return The column index.
     */
    public int getColumnIndex(Comparable columnKey) {
        List categories = getCategories();
        return categories.indexOf(columnKey);
    }

    /**
     * Returns a row index.
     *
     * @param rowKey  the row key.
     *
     * @return The row index.
     */
    public int getRowIndex(Comparable rowKey) {
        List seriesKeys = getSeries();
        return seriesKeys.indexOf(rowKey);
    }

    /**
     * Returns a list of the series in the dataset.
     * <P>
     * Supports the CategoryDataset interface.
     *
     * @return A list of the series in the dataset.
     */
    public List getRowKeys() {
        // the CategoryDataset interface expects a list of series, but
        // we've stored them in an array...
        if (this.seriesKeys == null) {
            return new java.util.ArrayList();
        }
        else {
            return Collections.unmodifiableList(Arrays.asList(this.seriesKeys));
        }
    }

    /**
     * Returns the name of the specified series.
     *
     * @param row  the index of the required row/series (zero-based).
     *
     * @return The name of the specified series.
     */
    public Comparable getRowKey(int row) {
        if ((row >= getRowCount()) || (row < 0)) {
            throw new IllegalArgumentException(
                    "The 'row' argument is out of bounds.");
        }
        return this.seriesKeys[row];
    }

    /**
     * Returns the number of categories in the dataset.  This method is part of 
     * the {@link CategoryDataset} interface.
     *
     * @return The number of categories in the dataset.
     */
    public int getColumnCount() {
        int result = 0;
        if (this.startData != null) {
            if (getSeriesCount() > 0) {
                result = this.startData[0].length;
            }
        }
        return result;
    }

    /**
     * Returns the number of series in the dataset (possibly zero).
     *
     * @return The number of series in the dataset.
     */
    public int getRowCount() {
        int result = 0;
        if (this.startData != null) {
            result = this.startData.length;
        }
        return result;
    }

}