ballwar.model
Class Ball

java.lang.Object
  ballwar.model.Ball

All Implemented Interfaces:

Observer

public class Ball
extends Object
implements Observer

An concrete circular ball that moves in a line with its given velocity and bounces off the walls of a rectangularly shaped container. A ball has a location, a radius, a mass, and environment and an update strategy.

Field Summary

private IBallCmd	_collisionCmd The command sent to the dispatcher to notify the other balls that they may have collided with this ball.
private Color	_color The color of the ball.
private IBallEnvironment	_env The ball's environment
private Point	_location The present location of the center of the ball.
private double	_mass The mass of the ball
private static double	_Nudge Percentage amount to "nudge" collided balls away from each other beyond their minimum distance.
private IPaintStrategy	_paintStrategy The paint strategy used by the ball
private int	_radius The radius of the ball.
private IUpdateStrategy	_strategy The update strategy used by the ball
private Point	_velocity The current velocity of the ball.

Constructor Summary

Ball(IBallEnvironment env, IUpdateStrategy strategy, IPaintStrategy pstrategy)
Constructor for a ball.

Method Summary

void	bounce() Checks if the ball needs to bounce off the wall of its container.
void	checkCollide(Ball aBall) Checks if this ball has collided with the given target ball.
void	collidedWith(Ball aBall, double distance, double deltaR) Called when this ball has moved and collided with the target ball.
void	collidedWithHelp(Ball aBall, double impx, double impy) Called when another ball has moved an collided with this target ball.
void	doKill() Kills th ball by removing it from the dispatcher.
Color	getColor() Returns the current color of this Ball.
IBallEnvironment	getEnv() Get the ball's environment
Point	getLocation() Returns the current center of this Ball.
double	getMass() Get the ball's mass
IPaintStrategy	getPaintStrategy() Returns the current paint strategy of this Ball
int	getRadius() Returns the current radius for this Ball.
IUpdateStrategy	getStrategy() Returns the current strategy of this Ball
Point	getVelocity() Returns the current velocity of this Ball.
void	kill() "Kills" this ball by delegating the request to the strategy.
void	paint(Graphics g) Paints the image of the ball onto a Graphics object using the current paint strategy.
void	setColor(Color color) Sets the color of this Ball to a given color.
void	setLocation(Point location) Sets the center of the ball to a new location.
void	setMass(double mass) Sets the ball's mass
void	setPaintStrategy(IPaintStrategy pstrategy) Sets the current strategy of this Ball to the given strategy
void	setRadius(int radius) Sets the radius of this Ball to a new radius.
void	setStrategy(IUpdateStrategy strategy) Sets the current update strategy of this Ball to the given strategy
void	setVelocity(Point velocity) Sets the velocity of this Ball to a new velocity.
void	update(Observable o, Object cmd) The update method called by the main ball Dispatcher to notify all the balls to perform the given command.
void	updateState(Graphics g) Updates the state of the ball by calling the strategy's updateState(), moving the ball as per its velocity, bouncing off the walls if necessary, and notifying all other balls that it may have collided with them.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

_env

private IBallEnvironment _env

The ball's environment

_location

private Point _location

The present location of the center of the ball.

_radius

private int _radius

The radius of the ball.

_velocity

private Point _velocity

The current velocity of the ball. Given in terms of an X and Y increment per update interval.

_color

private Color _color

The color of the ball.

_mass

private double _mass

The mass of the ball

_strategy

private IUpdateStrategy _strategy

The update strategy used by the ball

_paintStrategy

private IPaintStrategy _paintStrategy

The paint strategy used by the ball

_collisionCmd

private IBallCmd _collisionCmd

The command sent to the dispatcher to notify the other balls that they may have collided with this ball. Students to add initialization here using anonymous inner class. Should conform to these two specifications: 1. No action taken if the target is the same ball (same instance) as this ball. 2. If not the same ball, then this ball should checkCollide with the target ball, NOT the other way around. This is because the algorithms assume that the ball doing the checking is the one that just moved.

_Nudge

private static double _Nudge

Percentage amount to "nudge" collided balls away from each other beyond their minimum distance. This helps prevent re-colliding.

Constructor Detail

Ball

public Ball(IBallEnvironment env,
            IUpdateStrategy strategy,
            IPaintStrategy pstrategy)

Constructor for a ball. Calls the init method of the given strategy to initialize the ball.

Parameters:

env - The ball's environment

strategy - The update strategy used by the ball.

Method Detail

update

public void update(Observable o,
                   Object cmd)

The update method called by the main ball Dispatcher to notify all the balls to perform the given command. The given command is executed.

Specified by:

update in interface Observer

Parameters:

o - The Dispatcher that set the update request.

cmd - The IBallCmd that will be run.

updateState

public void updateState(Graphics g)

Updates the state of the ball by calling the strategy's updateState(), moving the ball as per its velocity, bouncing off the walls if necessary, and notifying all other balls that it may have collided with them. Finally, the ball is painted onto the given Graphics object.

Parameters:

g - The Graphics object to paint on.

bounce

public void bounce()

Checks if the ball needs to bounce off the wall of its container. Performs a perfectly elastic bounce, moving the ball back completely onto the drawing area if necessary.

setLocation

public void setLocation(Point location)

Sets the center of the ball to a new location.

Parameters:

location - the new center.

getLocation

public Point getLocation()

Returns the current center of this Ball.

Returns:

a Point representing the center of this Ball.

setRadius

public void setRadius(int radius)

Sets the radius of this Ball to a new radius.

Parameters:

radius -

getRadius

public int getRadius()

Returns the current radius for this Ball.

Returns:

the radius of this Ball.

setVelocity

public void setVelocity(Point velocity)

Sets the velocity of this Ball to a new velocity.

Parameters:

velocity - the new velocity for this Ball.

getVelocity

public Point getVelocity()

Returns the current velocity of this Ball.

Returns:

the current velocity of this Ball.

setColor

public void setColor(Color color)

Sets the color of this Ball to a given color.

Parameters:

color - the new color for this Ball.

getColor

public Color getColor()

Returns the current color of this Ball.

Returns:

the color of this Ball.

getStrategy

public IUpdateStrategy getStrategy()

Returns the current strategy of this Ball

Returns:

the IUpdateStrategy currently in use.

setPaintStrategy

public void setPaintStrategy(IPaintStrategy pstrategy)

Sets the current strategy of this Ball to the given strategy

Parameters:

strategy - The new IPaintStrategy to use.

getPaintStrategy

public IPaintStrategy getPaintStrategy()

Returns the current paint strategy of this Ball

Returns:

the IPaintStrategy currently in use.

setStrategy

public void setStrategy(IUpdateStrategy strategy)

Sets the current update strategy of this Ball to the given strategy

Parameters:

strategy - The new IUpdateStrategy to use.

paint

public void paint(Graphics g)

Paints the image of the ball onto a Graphics object using the current paint strategy.

Parameters:

g - a Graphics object.

kill

public void kill()

"Kills" this ball by delegating the request to the strategy.

doKill

public void doKill()

Kills th ball by removing it from the dispatcher. This will effectively remove the ball from the system.

getEnv

public IBallEnvironment getEnv()

Get the ball's environment

Returns:

the ball's environment

getMass

public double getMass()

Get the ball's mass

Returns:

The ball's mass

setMass

public void setMass(double mass)

Sets the ball's mass

Parameters:

mass - The mass value. Must be a positive, non-zero number.

checkCollide

public void checkCollide(Ball aBall)

Checks if this ball has collided with the given target ball. Calls collidedWith() if it has collided.

Parameters:

aBall - The target ball.

collidedWith

public void collidedWith(Ball aBall,
                         double distance,
                         double deltaR)

Called when this ball has moved and collided with the target ball. Recalculates the velocity assuming a perfectly elastic collision between to non-zero mass circular objects. The target ball's collidedWithHelp() method is called and then the strategy's updateCollision() method is called.

Parameters:

aBall - The target ball

distance - The actual, current separation distance between the two balls' centers.

deltaR - The difference in distance between the minimum allowed separation of the two balls and the actual separation.

collidedWithHelp

public void collidedWithHelp(Ball aBall,
                             double impx,
                             double impy)

Called when another ball has moved an collided with this target ball. Adjusts this ball's velocity as per the given momentum impulse parameters. This ball's strategy's collisionUpdate() method is called after the velocity is modified.

Parameters:

aBall - The ball that moved and collided with this ball.

impx - The x-component of the collision impulse

impy - The y-component of the collision impulse