carousel.java

design pattern in java

package com.oozinoz.carousel;

import java.awt.event.*;
import javax.swing.*;
import java.util.Observable;

/*
 * Copyright (c) 2001 Steven J. Metsker.
 * 
 * Steve Metsker makes no representations or warranties about
 * the fitness of this software for any particular purpose, 
 * including the implied warranty of merchantability.
 *
 * Please use this software as you wish with the sole
 * restriction that you may not claim that you wrote it.
 */
/**
 * Model the behavior of a carousel, the machine that will
 * send our door object clicks.
 * 
 * @author Steven J. Metsker
 * @see ShowCarousel
 */
public class Carousel
extends Observable implements ActionListener 
{

	private double percentClosed = 1.00;
	private Timer heartbeatTimer;
	private Timer timeoutTimer;


	
	// Carousel uses the following states, not to be confused 
	// with ones we create for the Door classes; Carousel is 
	// a black box to us
	public static final int CLOSED = -1;
	public static final int OPENING = -2;
	public static final int OPEN = -3;
	public static final int CLOSING = -4;
	public static final int STAYOPEN = -5;
	//
	private int state = CLOSED;
/**
 * Respond to one of two timers, our heartbeat or the
 * timeout timer.
 */
public void actionPerformed(ActionEvent e)
{
	Object source = e.getSource();
	if (source.equals(heartbeatTimer()))
	{
		heartbeat();
	}
	if (source.equals(timeoutTimer()))
	{
		timeout();
	}
}
/**
 * The user clicked our button. React accordingly
 * and let the Door object know.
 */
public void click()
{
	if (state == CLOSED)
	{
		this.state = OPENING;
	}
	else if (state == OPENING || state == STAYOPEN)
	{
		this.state = CLOSING;
	}
	else if (state == OPEN)
	{
		this.state = STAYOPEN;
		timeoutTimer.stop();
	}
	else if (state == CLOSING)
	{
		this.state = OPENING;
	}
	setChanged();
	notifyObservers();
}
/**
 * Return a percentage showing how closed the
 * door is.
 */
public double getPercentClosed()
{
	return percentClosed;
}
/*
 * Update the simulated door.
 */
private void heartbeat()
{
	if (state == OPENING)
	{
		incrementPercentClosed(-.04);
		if (percentClosed <= 0.01)
		{
			this.state = OPEN;
			timeoutTimer().start();
		}
	}
	else if (state == CLOSING)
	{
		incrementPercentClosed(.04);
		if (percentClosed >= 0.99)
		{
			this.state = CLOSED;
		}
	}
}
/*
 * This timer makes the carousel seem alive.
 */
private Timer heartbeatTimer()
{
	if (heartbeatTimer == null)
	{
		heartbeatTimer = new Timer(400, this);
	}
	return heartbeatTimer;
}
private void incrementPercentClosed(double inc)
{
	percentClosed += inc;
	percentClosed = Math.min(1.0, percentClosed);
	percentClosed = Math.max(0.0, percentClosed);
	if (percentClosed >= 0.99)
	{
		state = CLOSED;
	}
	else if (percentClosed <= 0.01)
	{
		state = OPEN;
	}
	setChanged();
	notifyObservers();
}

/**
 * Start the timer that makes a carousel object
 * monitor the state of its door.
 */
public void start()
{
	heartbeatTimer().start();
}
/*
 * We got bored standing around with our door open.
 */
private void timeout()
{
	state = CLOSING;
	setChanged();
	notifyObservers();
}
/**
 * Insert the method's description here.
 * Creation date: (5/15/01 12:30:54 PM)
 * @param args java.lang.String[]
 */
private Timer timeoutTimer()
{
	if (timeoutTimer == null)
	{
		timeoutTimer = new Timer(2000, this);
		timeoutTimer.setRepeats(false);
	}
	return timeoutTimer;
}

/**
 * Return a textual description of the door's state.
 *
 * @return a textual description of the door's state
 */
public String status()
{
	switch (state)
	{
		case OPENING :
			return "Opening";
		case OPEN :
			return "Open";
		case CLOSING :
			return "Closing";
		case STAYOPEN :
			return "StayOpen";
		default :
			return "Closed";
	}
}
}