protected List data;

    /** The maximum number of items for the series. */
    private int maximumItemCount = Integer.MAX_VALUE;

    /** A flag that controls whether the items are automatically sorted. */
    private boolean autoSort;

    /** A flag that controls whether or not duplicate x-values are allowed. */
    private boolean allowDuplicateXValues;

    /**
     * Creates a new empty series.  By default, items added to the series will
     * be sorted into ascending order by x-value, and duplicate x-values will
     * be allowed (these defaults can be modified with another constructor.
     *
     * @param key  the series key (<code>null</code> not permitted).
     */
    public XYSeries(Comparable key) {
        this(key, true, true);