Particle.java

/*
  Copyright 2006 by Sean Luke and George Mason University
  Licensed under the Academic Free License version 3.0
  See the file "LICENSE" for more information
*/

package sim.app.tutorial3;
import sim.engine.*;
import sim.util.*;

/** A bouncing particle. */

public class Particle implements Steppable
    {
    private static final long serialVersionUID = 1;

    public boolean randomize = false;
    public int xdir;  // -1, 0, or 1
    public int ydir;  // -1, 0, or 1
    
    public Particle(int xdir, int ydir)
        {
        this.xdir = xdir;
        this.ydir = ydir;
        }

    public void step(SimState state)
        {
        Tutorial3 tut = (Tutorial3)state;
        
        // We could just store my location internally, but for purposes of
        // show, let's get my position out of the particles grid
        Int2D location = tut.particles.getObjectLocation(this);

        // leave a trail
        tut.trails.field[location.x][location.y] = 1.0;
        
        // Randomize my direction if requested
        if (randomize)
            {
            xdir = tut.random.nextInt(3) - 1;
            ydir = tut.random.nextInt(3) - 1;
            randomize = false;
            }
        
        // move
        int newx = location.x + xdir;
        int newy = location.y + ydir;
        
        // reverse course if hitting boundary
        if (newx < 0) { newx++; xdir = -xdir; }
        else if (newx >= tut.trails.getWidth()) {newx--; xdir = -xdir; }
        if (newy < 0) { newy++ ; ydir = -ydir; }
        else if (newy >= tut.trails.getHeight()) {newy--; ydir = -ydir; }
        
        // set my new location
        Int2D newloc = new Int2D(newx,newy);
        tut.particles.setObjectLocation(this,newloc);
        
        // randomize everyone at that location if need be
        Bag p = tut.particles.getObjectsAtLocation(newloc);
        if (p.numObjs > 1)
            {
            for(int x=0;x<p.numObjs;x++)
                ((Particle)(p.objs[x])).randomize = true;
            }
        }
    }