public final class DatasetRenderingOrder implements Serializable {

    /** For serialization. */
    private static final long serialVersionUID = -600593412366385072L;    

    /** 
     * Render datasets in the order 0, 1, 2, ..., N-1, where N is the number 
     * of datasets. 
     */
    public static final DatasetRenderingOrder FORWARD
            = new DatasetRenderingOrder("DatasetRenderingOrder.FORWARD");

    /** 
     * Render datasets in the order N-1, N-2, ..., 2, 1, 0, where N is the 
     * number of datasets. 
     */
    public static final DatasetRenderingOrder REVERSE
            = new DatasetRenderingOrder("DatasetRenderingOrder.REVERSE");

    /** The name. */
    private String name;

    /**
     * Private constructor.
     *
     * @param name  the name.
     */
    private DatasetRenderingOrder(String name) {
        this.name = name;
    }

    /**
     * Returns a string representing the object.
     *
     * @return The string (never <code>null</code>).
     */
    public String toString() {
        return this.name;
    }

    /**
     * Returns <code>true</code> if this object is equal to the specified 
     * object, and <code>false</code> otherwise.
     *
     * @param obj  the object (<code>null</code> permitted).
     *
     * @return A boolean.
     */
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (!(obj instanceof DatasetRenderingOrder)) {
            return false;
        }
        DatasetRenderingOrder order = (DatasetRenderingOrder) obj;
        if (!this.name.equals(order.toString())) {
            return false;
        }
        return true;
    }
    
    /**
     * Returns a hash code for this instance.
     * 
     * @return A hash code.
     */
    public int hashCode() {
        return this.name.hashCode();
    }
    
    /**
     * Ensures that serialization returns the unique instances.
     * 
     * @return The object.
     * 
     * @throws ObjectStreamException if there is a problem.
     */
    private Object readResolve() throws ObjectStreamException {
        if (this.equals(DatasetRenderingOrder.FORWARD)) {
            return DatasetRenderingOrder.FORWARD;
        }
        else if (this.equals(DatasetRenderingOrder.REVERSE)) {
            return DatasetRenderingOrder.REVERSE;
        }      
        return null;