Simulation Simplified
15. Priority Queues
Class edu.rit.sim.Event

//******************************************************************************
//
// File:    Event.java
// Package: edu.rit.sim
// Unit:    Class edu.rit.sim.Event
//
// This Java source file is copyright (C) 2011 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************

package edu.rit.sim;

/**
 * Class Event is the abstract base class for an event in a discrete event
 * simulation.
 *
 * @author  Alan Kaminsky
 * @version 29-Jul-2011
 */
public abstract class Event
   {

// Hidden data members.

   // Simulation in which this event occurs.
   Simulation sim;

   // Simulation time of this event.
   double time;

// Exported constructors.

   /**
    * Construct a new event.
    */
   public Event()
      {
      }

// Exported operations.

   /**
    * Returns the simulation in which this event occurs.
    *
    * @return  Simulation.
    */
   public final Simulation simulation()
      {
      return sim;
      }

   /**
    * Returns this event's simulation time, the time when this event is
    * scheduled to take place.
    *
    * @return  Simulation time.
    */
   public final double time()
      {
      return time;
      }

   /**
    * Schedule the given event to be performed at the given time in this
    * event's simulation.
    *
    * @param  t      Simulation time for <TT>event</TT>.
    * @param  event  Event to be performed.
    *
    * @exception  IllegalArgumentException
    *     (unchecked exception) Thrown if <TT>t</TT> is less than the current
    *     simulation time.
    * @exception  NullPointerException
    *     (unchecked exception) Thrown if <TT>event</TT> is null.
    */
   public final void doAt
      (double t,
       Event event)
      {
      sim.doAt (t, event);
      }

   /**
    * Schedule the given event to be performed at a time <TT>dt</TT> in the
    * future (at current simulation time + <TT>dt</TT>) in this event's
    * simulation.
    *
    * @param  dt     Simulation time delta for <TT>event</TT>.
    * @param  event  Event to be performed.
    *
    * @exception  IllegalArgumentException
    *     (unchecked exception) Thrown if <TT>dt</TT> is less than zero.
    * @exception  NullPointerException
    *     (unchecked exception) Thrown if <TT>event</TT> is null.
    */
   public final void doAfter
      (double dt,
       Event event)
      {
      sim.doAfter (dt, event);
      }

   /**
    * Perform this event. Called by the {@linkplain Simulation} when the
    * simulation time equals the time when this event is scheduled to take
    * place.
    */
   public abstract void perform();

   }