/* * Action.java * The package reservation contains the different class allowing to choose the action to realise. */package reservation;/** * This class uniform the way to call each sub-class (Create, Reserve, Cancel, Lists, Identify) that processes the commands. * It delegates to the sub-class the implementation of the function execute (), usage () and check (). * Also it masks the machinery and helps the developer who want to reuse the program. * @author Texier Mathieu and Frederic Bidon */public interface Action {    /**     * Proceed the execution of the action     * @param arg The argument of the coresponding function     * @return The apropriate string message     * @throws Exception When an error occurs     */        String execute (String[] arg) throws Exception;    /**     * Maximal number of argument for the command mode     */        static public final int NUMBER_ARGUMENT_MAX = 100;    /**     * The instance of the Flight System     */        reservation.system.FlightSystem fs = reservation.system.FlightSystem.getInstance();}