FruitOption
    "No fruit chosen"
    Orange
    Banana

AnimalOption
    "No animal chosen"
    Dog
    Cat

/**
 * Returns the display value for the null value.
 * The default behavior is to look the value up by
 * using the key retrieved by calling: <code>getNullValidKey()</code>.
 *
 * @return The value to display for null
 */
protected String getNullValidDisplayValue() {
    String option =
            getLocalizer().getStringIgnoreSettings(getNullValidKey(), this, null, null);
    if (Strings.isEmpty(option)) {
        option = getLocalizer().getString("nullValid", this, "");
    }
    return option;
}

/**
 * Return the localization key for the nullValid value
 *
 * @return getId() + ".nullValid"
 */
protected String getNullValidKey() {
    return getId() + ".nullValid";
}

/**
 * Returns the display value if null is not valid but is selected.
 * The default behavior is to look the value up by using the key
 * retrieved by calling: <code>getNullKey()</code>.
 *
 * @return The value to display if null is not valid but is
 *     selected, e.g. "Choose One"
 */
protected String getNullKeyDisplayValue() {
    String option =
            getLocalizer().getStringIgnoreSettings(getNullKey(), this, null, null);

    if (Strings.isEmpty(option)) {
        option = getLocalizer().getString("null", this, CHOOSE_ONE);
    }
    return option;
}

/**
 * Return the localization key for null value
 *
 * @return getId() + ".null"
 */
protected String getNullKey() {
    return getId() + ".null";
}