public final class XYCoordinateType implements Serializable {
    
    /** The (x, y) coordinates represent a point in the data space. */
    public static final XYCoordinateType DATA 
            = new XYCoordinateType("XYCoordinateType.DATA");

    /** 
     * The (x, y) coordinates represent a relative position in the data space. 
     * In this case, the values should be in the range (0.0 to 1.0).
     */
    public static final XYCoordinateType RELATIVE 
            = new XYCoordinateType("XYCoordinateType.RELATIVE");

    /** 
     * The (x, y) coordinates represent indices in a dataset. 
     * In this case, the values should be in the range (0.0 to 1.0).
     */
    public static final XYCoordinateType INDEX 
            = new XYCoordinateType("XYCoordinateType.INDEX");

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

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

    /**
     * Returns a string representing the object.
     *
     * @return The string.
     */
    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 other object.
     *
     * @return A boolean.
     */
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (!(obj instanceof XYCoordinateType)) {
            return false;
        }
        XYCoordinateType order = (XYCoordinateType) obj;
        if (!this.name.equals(order.toString())) {
            return false;
        }
        return true;
    }
   
    /**
     * 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(XYCoordinateType.DATA)) {
            return XYCoordinateType.DATA;
        }
        else if (this.equals(XYCoordinateType.RELATIVE)) {
            return XYCoordinateType.RELATIVE;
        }     
        else if (this.equals(XYCoordinateType.INDEX)) {
            return XYCoordinateType.INDEX;
        }     
        return null;