// Class Botpackage sim.app.keepaway;import java.awt.*;import sim.portrayal.*;import sim.util.*;import sim.engine.*;public /*strictfp*/ class Bot extends Entity implements Steppable    {    public Bot( final double x, final double y, Color c)        {        super(x,y,2,c);        }    public void draw(Object object,  final Graphics2D g, final DrawInfo2D info )        {        // draw the circle        super.draw(object, g,info);                // draw our line as well                final double width = info.draw.width * radius * 2;        final double height = info.draw.height * radius * 2;            /*          final int x = (int)(info.draw.x - width / 2.0);          final int y = (int)(info.draw.y - height / 2.0);          final int w = (int)(width);          final int h = (int)(height);          g.setColor(c);          g.fillOval(x,y,w,h);        */                g.setColor(Color.white);        double d = velocity.angle();        g.drawLine((int)info.draw.x,                   (int)info.draw.y,                   (int)(info.draw.x) + (int)(width/2 * /*Strict*/Math.cos(d)),                   (int)(info.draw.y) + (int)(height/2 * /*Strict*/Math.sin(d)));        }     public Vector2D getForces( final Keepaway keepaway)        {        Bag objs = keepaway.fieldEnvironment.getObjectsWithinDistance(new Double2D(loc.x, loc.y), 100);        double dist = 0;        Vector2D sumVector = new Vector2D(0,0);        Vector2D tempVector = new Vector2D(0,0);                //http://www.martinb.com/physics/dynamics/collision/twod/index.htm        double mass1;        double mass2;        for(int x=0; x<objs.numObjs; x++)            {            if(objs.objs[x] != this)                {                               dist = ((Entity)objs.objs[x]).loc.getDistTo(loc);                                    if((((Entity)objs.objs[x]).radius + radius)*1.25 > dist)  // collision!                    {                    // 10% chance of kicking the ball, if it's a ball                    // and kicking is not especially interesting.. its just accelerated impact                    if(objs.objs[x] instanceof Ball && keepaway.random.nextDouble() < .1)                        {                        tempVector = loc.subtract(((Entity)objs.objs[x]).loc);                        tempVector.setLength(2.0);                        ((Entity)objs.objs[x]).velocity.x += -tempVector.x;                        ((Entity)objs.objs[x]).velocity.y += -tempVector.y;                        }                    else        // else just ram it...                        {               // shouldnt matter what type of object collision occurrs with                        tempVector.x = 0;                        tempVector.y = 0;                                                mass1 = mass - ((Entity)objs.objs[x]).mass;                        mass1 /= (mass + ((Entity)objs.objs[x]).mass);                                                mass2 = 2 * ((Entity)objs.objs[x]).mass;                        mass2 /= (mass + ((Entity)objs.objs[x]).mass);                                                // self = object a                        tempVector.x = velocity.x * mass1 + ((Entity)objs.objs[x]).velocity.x * mass2;                        tempVector.y = velocity.y * mass1 + ((Entity)objs.objs[x]).velocity.y * mass2;                                                // collided object = object                         ((Entity)objs.objs[x]).bump.x = velocity.x * mass2 - ((Entity)objs.objs[x]).velocity.x * mass1;                        ((Entity)objs.objs[x]).bump.y = velocity.y * mass2 - ((Entity)objs.objs[x]).velocity.y * mass1;                                                //sumVector = sumVector.add(tempVector);                        velocity.x = tempVector.x;                        velocity.y = tempVector.y;                        }                    }                else if(objs.objs[x] instanceof Ball)                    {                    // if we didn't hit the ball, we want to go towards it                    tempVector = new Vector2D(0,0);                    tempVector = ((Entity)objs.objs[x]).loc.subtract(loc);                    tempVector = tempVector.setLength(0.5);                    sumVector = sumVector.add(tempVector);                    }                }            }        // bump forces        sumVector = sumVector.add(bump);        bump.x = 0;        bump.y = 0;        return sumVector;        }     public void step( final SimState state )        {        Keepaway keepaway = (Keepaway)state;                // get force        Vector2D force = getForces(keepaway);                // acceleration = f/m        Vector2D accel = new Vector2D(force.x/mass,force.y/mass);                // v = v + a        velocity = velocity.add(accel);        capVelocity();                // L = L + v        Vector2D newLoc = new Vector2D( loc.x + velocity.x, loc.y + velocity.y);                // is new location valid?        if(isValidMove(keepaway, newLoc))            loc = newLoc;                keepaway.fieldEnvironment.setObjectLocation(this, new Double2D(loc.x, loc.y));        }    }