public class StandardXYSeriesLabelGenerator implements XYSeriesLabelGenerator, 
        Cloneable, PublicCloneable, Serializable {

    /** For serialization. */
    private static final long serialVersionUID = 1916017081848400024L;
    
    /** The default item label format. */
    public static final String DEFAULT_LABEL_FORMAT = "{0}";
    
    /** The format pattern. */
    private String formatPattern;

    /**
     * Creates a default series label generator (uses 
     * {@link #DEFAULT_LABEL_FORMAT}).
     */
    public StandardXYSeriesLabelGenerator() {
        this(DEFAULT_LABEL_FORMAT);
    }
    
    /**
     * Creates a new series label generator.
     * 
     * @param format  the format pattern (<code>null</code> not permitted).
     */
    public StandardXYSeriesLabelGenerator(String format) {
        if (format == null) {
            throw new IllegalArgumentException("Null 'format' argument.");
        }
        this.formatPattern = format;
    }

    /**
     * Generates a label for the specified series.  This label will be
     * used for the chart legend.
     * 
     * @param dataset  the dataset (<code>null</code> not permitted).
     * @param series  the series.
     * 
     * @return A series label.
     */
    public String generateLabel(XYDataset dataset, int series) {
        if (dataset == null) {
            throw new IllegalArgumentException("Null 'dataset' argument.");
        }
        String label = MessageFormat.format(
            this.formatPattern, createItemArray(dataset, series)
        );
        return label;
    }

    /**
     * Creates the array of items that can be passed to the 
     * {@link MessageFormat} class for creating labels.
     *
     * @param dataset  the dataset (<code>null</code> not permitted).
     * @param series  the series (zero-based index).
     *
     * @return The items (never <code>null</code>).
     */
    protected Object[] createItemArray(XYDataset dataset, int series) {
        Object[] result = new Object[1];
        result[0] = dataset.getSeriesKey(series).toString();
        return result;
    }

    /**
     * Returns an independent copy of the generator.  This is unnecessary, 
     * because instances are immutable anyway, but we retain this 
     * behaviour for backwards compatibility.
     * 
     * @return A clone.
     * 
     * @throws CloneNotSupportedException if cloning is not supported.
     */
    public Object clone() throws CloneNotSupportedException { 
        return super.clone();
    }
    
    /**
     * Tests this object for equality with an arbitrary object.
     *
     * @param obj  the other object (<code>null</code> permitted).
     *
     * @return A boolean.
     */
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (!(obj instanceof StandardXYSeriesLabelGenerator)) {
            return false;
        }
        StandardXYSeriesLabelGenerator that 
                = (StandardXYSeriesLabelGenerator) obj;
        if (!this.formatPattern.equals(that.formatPattern)) {
            return false;
        }
        return true;
    }
    
    /**
     * Returns a hash code for this instance.
     * 
     * @return A hash code.
     */
    public int hashCode() {
        int result = 127;
        result = HashUtilities.hashCode(result, this.formatPattern);
        return result;