antapplet.java

Java source code for the Ant Colony Optimization Problem.

package jwo.jpss.ants;      // Part of the ant simulation package.
import java.applet.Applet;	// Required for applet functionality.
import java.awt.*;          // For GUI.
import jwo.jpss.spatial.*;  // For spatial classes.
import java.util.*;         // For Java vector class.

//  **************************************************************
/** Applet front end to the Ants in the Garden simulator.
  * @author   Jo Wood.
  * @version  1.2, 26th July, 2001
  */
//  **************************************************************

public class AntApplet extends Applet 
                    implements GraphicsListener, Runnable
{ 
    // ------------------- Object variables ---------------------
    
    private Thread evolution;     // Evolutionary process.
    private Garden garden;        // Garden containing ants.

    private Image    offscreenImage;    // Double-buffering objects.
    private Graphics offscreenGraphics;
          	
    // -------------------- Starter methods ---------------------
   
    /** Initialises the applet within which the ants may be observed.
      */
    public void init()
    {	
        evolution = new Thread(this);  // Make dynamic evolution a thread.
	    Dimension appletSize = getSize();	

	    // Create an offscreen Image and garden on which to draw.		
        offscreenImage = createImage(appletSize.width,appletSize.height);
        offscreenGraphics = offscreenImage.getGraphics(); 
        garden = new Garden(new Footprint(0,0,appletSize.width,appletSize.height));
        garden.addGraphicsListener(this);
    }
    
    /** Starts off the ant simulation or resumes it if window has been deiconified
      * after being iconified. 
      */
    public void start()
    {  
        evolution.start();
    }
    		 
    // ---------------------- Methods ------------------------
   
    /** Allows the simulator to draw in this applet using double buffering.
      * @param g Graphics context within which to draw.
      */
    public void paint(Graphics g) 
    {
	    garden.paint(offscreenGraphics);
        g.drawImage(offscreenImage,1,1,null);
    }

    /** Provides a description of this applet for the embedding browser.     
      * @return Message describing the applet.
      */
    public String getAppletInfo() 
    {
        return "Ants in the Garden - A Simulation by Jo Wood, 2001";
    }

    // ---------------- Implemented  methods -----------------
    
    /** Controls the evolution of the simulation as a threaded
      * process.
      */ 
    public void run()
    {
        garden.startEvolution();	
    } 

    /** Stops the ant simulation, either temporarily if the window is minimised,
      * or permanently if it is closed.
      */
    public void stop()
    {  
        garden.stopEvolution();
        showStatus("Ant simulator paused");
        super.stop();
    }
     
    /** Redraws any graphics that need updating.
      */
    public void redrawGraphics()
    {
        Graphics g = getGraphics();
    	
        if (g != null)
            paint(g);
    }

    /** Checks that the given spatial object can be drawn 
      * in this applet.
      * @param spObject Spatial object we wish to draw.
      * @return True if the spatial object can be drawn.
      */
    public boolean canDraw(SpatialObject spObject)
    {
        if (garden.compare(spObject) == SpatialModel.ENCLOSES)
            return true;
        else
            return false;
    }

    /** Reports the list of SpatialObjects assoicated with the given
      * spatial object (within, matching, overlapping or containing). 
      * @param spObject spatial object with which to compare.
      * @return List of spatial objects in contact with the given one.
      */
    public Vector objectsAt(SpatialObject spObject)
    {
        return garden.objectsAt(spObject);
    } 

    /** Displays the given message in the applet. Some browsers may
      * choose to ignore this request.
      * @param message Message to display.
      */
    public void displayMessage(String message)
    {
    	showStatus(message);
    }
}