// This example is from the book Developing Java Beans by Robert Englander. 
// Copyright (c) 1997 O'Reilly & Associates.
// You may study, use, modify, and distribute this example for any purpose.
// This example is provided WITHOUT WARRANTY either expressed or implied.

// Chapter 11 -- The VisualTemperature class

package BeansBook.Simulator;

import java.beans.*;
import java.awt.*;

// the temperature bean class definition
public class VisualTemperature extends Panel
   implements TemperaturePulseListener,  // listends for temperature pulses
              java.io.Serializable       // declare Serializable
{
   // support object for bound property listeners
   protected PropertyChangeSupport boundSupport;
   
   // the current temperature
   protected double theTemperature = 22.0;
   
   // constructor
   public VisualTemperature()
   {
      // construct the support object
      boundSupport = new PropertyChangeSupport(this);
   }
   
   // add a property change listener
   public void addPropertyChangeListener(PropertyChangeListener l)
   {
      // defer to the support object
      boundSupport.addPropertyChangeListener(l);
   }
   
   // remove a property change listener
   public void removePropertyChangeListener(PropertyChangeListener l)
   {
      // defer to the support object
      boundSupport.removePropertyChangeListener(l);
   }
   
   // get the value of the Temperature property
   public double getTemperature()
   {
      return theTemperature;
   }
   
   // set the value of the Temperature property
   public void setTemperature(double t)
   {
      // don't bother if the value didn't change
      if (t == theTemperature)
      {
         return;
      }

      // save the old value
      Double old = new Double(theTemperature);
      
      // save the new value         
      theTemperature = t;
      
      // fire the property change event
      boundSupport.firePropertyChange("Temperature", old, new Double(t));
   }
   
   // handle a temperature pulse event
   public void temperaturePulse(TemperaturePulseEvent evt)
   {
      // get the pulse temperature
      double p = evt.getPulseTemperature();
      
      // get the current temp
      double c = getTemperature();
      
      // if the pulse temperature is greater than the current temperature
      if (p > c)
      {
         // only change if the difference is more than 1
         if ((p - c) >= 1.0)
         { 
            // add 1 to the current temperature
            setTemperature(c + 1.0);
         }
      }
      else if (p < c) // pulse less than the current temperature
      {
         // only change if the difference is more than 1
         if ((c - p) >= 1.0)
         {
            // subtract 1 from the current temperature
            setTemperature(c - 1.0);
         }
      }
   }
   
   // take a temperature pulse by a direct method call
   public void directTemperaturePulse(double pulse)
   {
      // emulate a regular temperature pulse
      temperaturePulse(new TemperaturePulseEvent(null, pulse));
   }
}