public void setAlertMessage(final String MESSAGE) {
        if (null == alertMessage) {
            _alertMessage = MESSAGE;
            fireTileEvent(ALERT_EVENT);
        } else {
            if (!alertMessage.isBound()) {
                alertMessage.set(MESSAGE);
            }
        }
    }
Defines the text that could be used in a tooltip as an
alert message.
@param MESSAGE
src/main/java/eu/hansolo/tilesfx/Tile.java