animator4
Class Animator

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--java.awt.Panel
                    |
                    +--java.applet.Applet
                          |
                          +--edu.davidson.tools.SApplet
                                |
                                +--animator4.Animator

All Implemented Interfaces:

javax.accessibility.Accessible, java.awt.image.ImageObserver, java.awt.MenuContainer, java.io.Serializable

public class Animator

extends SApplet

Animator is part of the Davidson College Physlets project. It is designed to animate shapes or images on the screen. Objects can move along a predefined trajectory or in response to a force.

The following embedding parameters are defined:

Parameter	Value	Description
FPS	10	Frames per second.
dt	0.1	Animation time step per frame.
ShowControls	true	Show VCR buttons at bottom of applet.
GridUnit	1.0	The grid spacing. A value of 0 will suppress the grid.
PixPerUnit	10	Conversion factor from pixel units to world units.

Various objects in Animator implement the data source interface. This interface, SDataSource, enables inter-applet data passing between Physlets.

Object	Identifier	Variables
images	id=addImage(String file,String xStr,String yStr)	t, x, y, vx, vy, ax, ay, m
All shapes: circle, rectangle, box, arrow, etc.	The id is returned when an object is created using an add method.	t, x, y, vx, vy, ax, ay, m
clock	id=getClockID()	t
ensemble	id=getEnsembleID()	t, xcm, ycm, px, py , m , ke

See Also:

Serialized Form

Fields inherited from class edu.davidson.tools.SApplet

clock, dataConnections, dataListeners, dataSources, lock

Fields inherited from class java.awt.Component

BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT

Constructor Summary

Animator()

Method Summary

int	addObject(java.lang.String name, java.lang.String parList) Create an object and add it to the Physlet.
void	forward() Start the animation.
double	getAnimationTime() Get the animation time.
java.lang.String	getAppletInfo()
int	getEnsembleID() Get the id for the ensemble of objects.
double	getFx(int id) Get the x component of the force acting on an object.
double	getFy(int id) Get the y component of the force acting an object.
java.lang.String	getParameter(java.lang.String key, java.lang.String def)
java.lang.String[][]	getParameterInfo()
double	getVX(int id) Get the x velocity of an object.
double	getVY(int id) Get the y velocity of on an object.
double	getX(int id) Get the x position of an object.
double	getY(int id) Get the y position of an object.
void	init()
static void	main(java.lang.String[] args)
void	pause() Pause the animation.
void	reset() Clear data from all dataConnections and reset the animation time to 0.
void	reverse() Reverse the direction of the time step in the animation.
boolean	setAnimationSlave(int masterID, int slaveID) Force an object to follow another object on the screen.
void	setAnimationTime(double time) Set the animation time.
void	setAutoRefresh(boolean auto) Force the applet to repaint whenever any object changes its properties.
int	setCaption(java.lang.String s) Add a caption to the applet.
void	setCollisionMessage(java.lang.String msg) Display a message in the yellow message box.
boolean	setConstrainR(int id, double r, double x, double y) Constrain the motion of the test charges to a circular path.
boolean	setConstrainX(int id, double x, double min, double max) Constrain the motion of the test charges to a path of constant x.
boolean	setConstrainY(int id, double y, double min, double max) Constrain the motion of the test charges to a path of constant y.
boolean	setCoordinateOffset(int id, int xOff, int yOff) Offset the object's coordinates on the screen.
void	setDampOnMousePressed(boolean damp) Set the velocity of an object to zero if it is being dragged.
void	setDefault() Set default values and deletes all data connections.
boolean	setDisplayOffset(int id, int xOff, int yOff) Offset the object's position on the screen from its default drawing position.
boolean	setDragable(int id, boolean canDrag) Make the object with the given id dragable.
boolean	setFont(int id, java.lang.String family, int style, int size) change the object's font for any text4 that is displayed.
boolean	setFootPrints(int id, int n) Set the trail to leave footprints as the charge moves.
boolean	setForce(int id, java.lang.String fxStr, java.lang.String fyStr, double x0, double y0, double vx0, double vy0) Set the Force on a particle.
boolean	setFormat(int id, java.lang.String fstr) Change the object's format for the display of numeric data.
boolean	setGhost(int id, boolean ghost) Have the charge draw ghost images as it moves.
void	setGridUnit(double gu) Set the grid spacing in world, i.e., not pixel, units.
boolean	setMass(int id, double m) Set the mass of an object.
void	setMessage(java.lang.String msg) Display a message in the yellow message box.
void	setOneShot(double min, double max, java.lang.String msg) Set the applet to run for a fixed interval, stop, and display a message.
boolean	setOnScreenSize(int id, int size) Set a size parameter for an object.
boolean	setPaintBeforeGrid(int id, boolean before) Have the object draw itself before the grid is drawn.
void	setPixPerUnit(int pu) Set the pixels per unit.
boolean	setRGB(int id, int r, int g, int b) Set the color of an object.
void	setShapeRGB(int r, int g, int b) Set the red, green, and blue color values for all subsequent drawing.
boolean	setShowAComponents(int id, boolean show) Have the object show its acceleration components.
boolean	setShowAVector(int id, boolean show) Have the object show its acceleration vector.
boolean	setShowConstraintPath(int id, boolean sc) Show the objects trajectory constraint if it exists.
boolean	setShowCoordinates(int id, boolean show) Have the object show its coordinates on screen.
boolean	setShowFComponents(int id, boolean show) Have the object show its force components.
boolean	setShowFVector(int id, boolean show) Have the object show its force vector.
boolean	setShowVComponents(int id, boolean show) Have the object show its velocity components.
boolean	setShowVVector(int id, boolean show) Have the object show its velocity vector.
boolean	setSpeed(int id, double speed) Change the speed of an object.
boolean	setSticky(int id, boolean sticky) Make the object sticky.
void	setTimeContinuous() Let the animation time increase indefinitely.
void	setTimeCycle(double max) Set a time loop for the animation from 0 to max.
void	setTimeDisplay(boolean show) Enable the time display in the applet window.
void	setTimeInterval(double min, double max) Set a time loop for the animation.
void	setTimeOneShot(double max, java.lang.String msg) Run the simulaiton one time.
void	setTimeVisibility(boolean visible) Enable the time display in the applet window.
void	setTolerance(double tol) Set the tolerance of the ODE solver.
boolean	setTrail(int id, int n) Enable an object to display its path as it moves.
boolean	setTrajectory(int id, java.lang.String xStr, java.lang.String yStr) Set the trajectory of an object on the screen.
boolean	setVisibility(int id, boolean show) Show the visibility of the object.
boolean	setVX(int id, double vx) Change the x component of the speed of an object.
boolean	setVY(int id, double vy) Change the y component of the speed of an object.
boolean	setX(int id, double x) Change the x of an object.
boolean	setY(int id, double y) Change the y of an object.
void	shiftPixOrigin(int xo, int yo) Shift the origin for all drawing.
void	start()
void	stepBack()
void	stepForward()
void	stepTimeBack() Step the time backward by dt.
void	stepTimeForward() Step the time by dt.
void	stop()
boolean	swapZOrder(int id1, int id2) Swap the drawing order on the screen.

Methods inherited from class edu.davidson.tools.SApplet

addDataListener, addDataSource, cleanupDataConnections, clearAllData, clearData, deleteDataConnection, deleteDataConnections, destroy, getClockID, getDataConnectionFromDL, getDataConnectionFromDS, getDataFromDS, getDataListener, getDataListener, getDataSource, getDataSource, getID, getRunningID, getSourceData, getSourceVariables, isAutoRefresh, isClockRunning, makeDataConnection, removeDataListener, removeDataSource, setClockContinous, setClockCycle, setClockOneShot, setClockTime, setConnectionBlock, setConnectionListener, setConnectionSmoothing, setConnectionSource, setConnectionStride, setDt, setFPS, setRunningID, setRunningID, startClock, stepClock, stepTime, stopClock, updateDataConnection, updateDataConnections, useMasterClock

Methods inherited from class java.applet.Applet

getAccessibleContext, getAppletContext, getAudioClip, getAudioClip, getCodeBase, getDocumentBase, getImage, getImage, getLocale, getParameter, isActive, newAudioClip, play, play, resize, resize, setStub, showStatus

Methods inherited from class java.awt.Panel

addNotify

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getInsets, getLayout, getListeners, getMaximumSize, getMinimumSize, getPreferredSize, insets, invalidate, isAncestorOf, layout, list, list, locate, minimumSize, paint, paintComponents, preferredSize, print, printComponents, remove, remove, removeAll, removeContainerListener, removeNotify, setCursor, setFont, setLayout, update, validate

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addPropertyChangeListener, addPropertyChangeListener, bounds, checkImage, checkImage, contains, contains, createImage, createImage, disable, dispatchEvent, enable, enable, enableInputMethods, getBackground, getBounds, getBounds, getColorModel, getComponentOrientation, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getInputContext, getInputMethodRequests, getLocation, getLocation, getLocationOnScreen, getName, getParent, getPeer, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isDisplayable, isDoubleBuffered, isEnabled, isFocusTraversable, isLightweight, isOpaque, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, setBackground, setBounds, setBounds, setComponentOrientation, setDropTarget, setEnabled, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

Animator

public Animator()

Method Detail

getParameter

public java.lang.String getParameter(java.lang.String key,
                                     java.lang.String def)

init

public void init()

Overrides:

init in class java.applet.Applet

start

public void start()

Overrides:

start in class java.applet.Applet

stop

public void stop()

Overrides:

stop in class java.applet.Applet

setAutoRefresh

public void setAutoRefresh(boolean auto)

Force the applet to repaint whenever any object changes its properties. Default is true. Set this value to false at the beginning of long scripts and then reset to true to avoid flashing.

Overrides:

setAutoRefresh in class SApplet

Parameters:

auto - The id of the object.

setCaption

public int setCaption(java.lang.String s)

Add a caption to the applet.

Parameters:

The - caption.

Returns:

The id of the caption.

setDragable

public boolean setDragable(int id,
                           boolean canDrag)

Make the object with the given id dragable.

Parameters:

id - of the object.

canDrag - Is the object dragable?

Returns:

true if successful false otherwise

setVisibility

public boolean setVisibility(int id,
                             boolean show)

Show the visibility of the object.

Parameters:

show - true will show object on screen

Returns:

true if successful false otherwise

setDefault

public void setDefault()

Set default values and deletes all data connections. pixPerUnit= PARAM value. gridUnit= PARAM value. time=0. shapeTrail=0. pixelOrigin=(0,0). caption=null. timeDisplay=tue;

Overrides:

setDefault in class SApplet

setMass

public boolean setMass(int id,
                       double m)

Set the mass of an object.

Parameters:

id - The id of the object.

m - The new mass.

Returns:

True if successful.

setCollisionMessage

public void setCollisionMessage(java.lang.String msg)

Display a message in the yellow message box.

Parameters:

msg - Message to display after the animation stops.

setMessage

public void setMessage(java.lang.String msg)

Display a message in the yellow message box.

Parameters:

msg - Message to display after the animation stops.

setAnimationSlave

public boolean setAnimationSlave(int masterID,
                                 int slaveID)

Force an object to follow another object on the screen.

Parameters:

masterID - The id of the master object.

slaveID - The id of the slave object.

Returns:

true if successful.

setShapeRGB

public void setShapeRGB(int r,
                        int g,
                        int b)

Set the red, green, and blue color values for all subsequent drawing. Color values must be in the range 0..255.

Parameters:

r - red.

g - green.

b - blue.

setRGB

public boolean setRGB(int id,
                      int r,
                      int g,
                      int b)

Set the color of an object.

Parameters:

id - The id of the object.

r - red

g - green

b - blue

Returns:

True if successful.

setOneShot

public void setOneShot(double min,
                       double max,
                       java.lang.String msg)

Set the applet to run for a fixed interval, stop, and display a message.

Parameters:

min - The starting time value for the loop

max - The ending time for the loop.

msg - Message to display after the animation stops.

See Also:

setTimeContinuous(), setTimeInterval(double, double)

setOnScreenSize

public boolean setOnScreenSize(int id,
                               int size)

Set a size parameter for an object. The effect of this parameter varies, or has no effect, depending on the object. For example, the size of a spring determines the number of coild and the size of a box determines the width of the walls.

Parameters:

id - The ID of the object.

size - The size of the object.

Returns:

boolean Returns true if successful.

setTimeCycle

public void setTimeCycle(double max)

Set a time loop for the animation from 0 to max. Animation will run continuously.

Overrides:

setTimeCycle in class SApplet

Parameters:

max - The ending time for the loop.

See Also:

setTimeContinuous(), setOneShot(double, double, java.lang.String), setTimeInterval(double, double)

setTimeInterval

public void setTimeInterval(double min,
                            double max)

Set a time loop for the animation. Animation will run continuously.

Parameters:

min - The starting time value for the loop

max - The ending time for the loop.

See Also:

setTimeContinuous(), setOneShot(double, double, java.lang.String)

setTimeContinuous

public void setTimeContinuous()

Let the animation time increase indefinitely. May overflow for very long times.

Overrides:

setTimeContinuous in class SApplet

See Also:

setTimeOneShot(double, java.lang.String), setTimeInterval(double, double), setOneShot(double, double, java.lang.String)

setTimeOneShot

public void setTimeOneShot(double max,
                           java.lang.String msg)

Run the simulaiton one time.

Overrides:

setTimeOneShot in class SApplet

Parameters:

max - Reset the simulation to t=0 when t>=max and stop the simulation.

string - the message to be displayed on the screen when the max time is reached.

setFootPrints

public boolean setFootPrints(int id,
                             int n)

Set the trail to leave footprints as the charge moves.

Parameters:

id - The id of the object.

n - The number of points to skip between trail footprints or ghost images.

Returns:

boolean True if successful.

setGhost

public boolean setGhost(int id,
                        boolean ghost)

Have the charge draw ghost images as it moves. Use footprints to set the spacing.

Parameters:

id - The id of the object.

ghost - Draw ghost?

Returns:

True if successful.

setTolerance

public void setTolerance(double tol)

Set the tolerance of the ODE solver. Default is on part in 1.0e-8.

Parameters:

tol -

setTrail

public boolean setTrail(int id,
                        int n)

Enable an object to display its path as it moves. Not all objects can show their path.

Parameters:

id - The id of the object.

n - Number of points in trail. n=0 disables the trail.

Returns:

boolean True if successful.

setTrajectory

public boolean setTrajectory(int id,
                             java.lang.String xStr,
                             java.lang.String yStr)

Set the trajectory of an object on the screen.

Parameters:

id - The ID of the thing.

xStr - The function x(t).

yStr - The function y(t).

Returns:

boolean True if the functions are valid and the trajectory has been set.

setForce

public boolean setForce(int id,
                        java.lang.String fxStr,
                        java.lang.String fyStr,
                        double x0,
                        double y0,
                        double vx0,
                        double vy0)

Set the Force on a particle.

Parameters:

id - The ID of the pole.

fxStr - A function of t, x, y, vx, vy, ax, ay, m.

fyStr - A function of t, x, y, vx, vy, ax, ay, m.

x0 - The initial value for x.

y0 - The initial value for y.

vx0 - The initial value for vx.

vy0 - The initial value for vy.

Returns:

True if the functions are valid and the trajectory has been set.

setPaintBeforeGrid

public boolean setPaintBeforeGrid(int id,
                                  boolean before)

Have the object draw itself before the grid is drawn.

Parameters:

id - The id of the object.

before - Paint before grid?

Returns:

True if successful.

setTimeDisplay

public void setTimeDisplay(boolean show)

Enable the time display in the applet window.

Parameters:

show - boolean Show the time?

setTimeVisibility

public void setTimeVisibility(boolean visible)

Enable the time display in the applet window.

Parameters:

boolean - Show the time?

setShowConstraintPath

public boolean setShowConstraintPath(int id,
                                     boolean sc)

Show the objects trajectory constraint if it exists.

Parameters:

sc - Show the path?

setShowCoordinates

public boolean setShowCoordinates(int id,
                                  boolean show)

Have the object show its coordinates on screen.

Parameters:

id - The id of the object.

show - Show the coordinates?

Returns:

True if successful.

setShowVComponents

public boolean setShowVComponents(int id,
                                  boolean show)

Have the object show its velocity components.

Parameters:

id - The id of the object.

show - Show the velocity?

Returns:

True if successful.

setShowFComponents

public boolean setShowFComponents(int id,
                                  boolean show)

Have the object show its force components.

Parameters:

id - The id of the object.

show - Show the force?

Returns:

True if successful.

setShowAComponents

public boolean setShowAComponents(int id,
                                  boolean show)

Have the object show its acceleration components.

Parameters:

id - The id of the object.

show - Show the acceleration?

Returns:

True if successful.

setShowVVector

public boolean setShowVVector(int id,
                              boolean show)

Have the object show its velocity vector.

Parameters:

id - The id of the object.

show - Show the velocity?

Returns:

True if successful.

setShowAVector

public boolean setShowAVector(int id,
                              boolean show)

Have the object show its acceleration vector.

Parameters:

id - The id of the object.

show - Show the acceleration?

Returns:

True if successful.

setShowFVector

public boolean setShowFVector(int id,
                              boolean show)

Have the object show its force vector.

Parameters:

id - The id of the object.

show - Show the force?

Returns:

True if successful.

setSticky

public boolean setSticky(int id,
                         boolean sticky)

Make the object sticky. A sticky object will stop the clock upon a collision with another sticky object. The sticky object must be moving under the action of forces. Objects that have trajectories will not stick.

Parameters:

id - The id of the object.

sticky - Sticky?

Returns:

True if successful.

setConstrainR

public boolean setConstrainR(int id,
                             double r,
                             double x,
                             double y)

Constrain the motion of the test charges to a circular path.

Parameters:

r - The r value.

x - The x coordinate of the center

y - The y coordinate of the center

Returns:

True if successful.

setConstrainX

public boolean setConstrainX(int id,
                             double x,
                             double min,
                             double max)

Constrain the motion of the test charges to a path of constant x.

Parameters:

x - The x value.

xmin - The minimum value of the range.

xmax - The maximum value of the range.

Returns:

True if successful.

setConstrainY

public boolean setConstrainY(int id,
                             double y,
                             double min,
                             double max)

Constrain the motion of the test charges to a path of constant y.

Parameters:

y - The y value.

ymin - The minimum value of the range.

ymax - The maximum value of the range.

Returns:

True if successful.

setCoordinateOffset

public boolean setCoordinateOffset(int id,
                                   int xOff,
                                   int yOff)

Offset the object's coordinates on the screen.

Parameters:

id - The id of the object.

xoff - The x offset.

yoff - The y offset.

Returns:

True if successful.

setDampOnMousePressed

public void setDampOnMousePressed(boolean damp)

Set the velocity of an object to zero if it is being dragged.

Parameters:

damp - the velocity?

setFont

public boolean setFont(int id,
                       java.lang.String family,
                       int style,
                       int size)

change the object's font for any text4 that is displayed.

Parameters:

id - The id of the object.

family - The font family: Helvetica, Times.

style - The style, 0=plain, 1=bold.

size - The size of the font;

Returns:

True if successful.

setFormat

public boolean setFormat(int id,
                         java.lang.String fstr)

Change the object's format for the display of numeric data. Us this method to control the number of significant digits in calculations with text objects. Use Unix printf conventions. For example fstr="%6.3f"

Parameters:

id - The id of the object.

fstr - the format string.

Returns:

True if successful.

setDisplayOffset

public boolean setDisplayOffset(int id,
                                int xOff,
                                int yOff)

Offset the object's position on the screen from its default drawing position.

Parameters:

id - The id of the object.

xoff - The x offset.

yoff - The y offset.

Returns:

True if successful.

setGridUnit

public void setGridUnit(double gu)

Set the grid spacing in world, i.e., not pixel, units. Zero will suppress the drawing of the grid.

Parameters:

gu - grid unit.

setPixPerUnit

public void setPixPerUnit(int pu)

Set the pixels per unit. This sets the scale for the animation.

Parameters:

pu - pixels per unit.

shiftPixOrigin

public void shiftPixOrigin(int xo,
                           int yo)

Shift the origin for all drawing. Shift is specified in pixels.

Parameters:

xo - x pixel shift.

yo - y pixel shift.

reset

public void reset()

Clear data from all dataConnections and reset the animation time to 0.

Overrides:

reset in class SApplet

See Also:

setAnimationTime(double)

setAnimationTime

public void setAnimationTime(double time)

Set the animation time.

Parameters:

time - The new time displayed inside the applet.

stepTimeForward

public void stepTimeForward()

Step the time by dt.

Overrides:

stepTimeForward in class SApplet

See Also:

SApplet.setDt(double)

stepForward

public void stepForward()

stepTimeBack

public void stepTimeBack()

Step the time backward by dt.

Overrides:

stepTimeBack in class SApplet

See Also:

SApplet.setDt(double)

stepBack

public void stepBack()

addObject

public int addObject(java.lang.String name,
                     java.lang.String parList)

Create an object and add it to the Physlet. The first argument is the name of the object to be added and the second is a comma-delimited list of parameters. For example, a circle can be added a follows:

addObject ("circle", "x = 0, y = -1.0, r = 10");

Parameters:

name - the type of object to be created.

parList - a list of parameters to be set

Returns:

double id of the object

swapZOrder

public boolean swapZOrder(int id1,
                          int id2)

Swap the drawing order on the screen.

Parameters:

id1 - The first id of a screen object.

id2 - The second id of a screen object.

Returns:

True if successful.

getEnsembleID

public int getEnsembleID()

Get the id for the ensemble of objects. This id can be used to access the ensemble as a data source.

Returns:

int The id of the ensemble containing all objects on the screen. Used as a data source.

reverse

public void reverse()

Reverse the direction of the time step in the animation.

Overrides:

reverse in class SApplet

forward

public void forward()

Start the animation.

Overrides:

forward in class SApplet

pause

public void pause()

Pause the animation.

Overrides:

pause in class SApplet

getAnimationTime

public double getAnimationTime()

Get the animation time.

Returns:

The time displayed inside the applet.

getX

public double getX(int id)

Get the x position of an object.

Parameters:

id - The id of the object.

setX

public boolean setX(int id,
                    double x)

Change the x of an object.

Parameters:

id - The id of the object.

speed - new x

Returns:

true if successful

getY

public double getY(int id)

Get the y position of an object.

Parameters:

id - The id of the object.

setY

public boolean setY(int id,
                    double y)

Change the y of an object.

Parameters:

id - The id of the object.

speed - new y

Returns:

true if successful

getVX

public double getVX(int id)

Get the x velocity of an object.

Parameters:

id - The id of the object.

setVX

public boolean setVX(int id,
                     double vx)

Change the x component of the speed of an object.

Parameters:

id - The id of the object.

speed - new vx

Returns:

true if successful

getVY

public double getVY(int id)

Get the y velocity of on an object.

Parameters:

id - The id of the object.

setVY

public boolean setVY(int id,
                     double vy)

Change the y component of the speed of an object.

Parameters:

id - The id of the object.

speed - new vy

Returns:

true if successful

setSpeed

public boolean setSpeed(int id,
                        double speed)

Change the speed of an object. Direction of motion remains unchanged.

Parameters:

id - The id of the object.

speed - new speed

Returns:

true if successful

getFx

public double getFx(int id)

Get the x component of the force acting on an object.

Parameters:

id - The id of the object.

getFy

public double getFy(int id)

Get the y component of the force acting an object.

Parameters:

id - The id of the object.

getAppletInfo

public java.lang.String getAppletInfo()

Overrides:

getAppletInfo in class java.applet.Applet

getParameterInfo

public java.lang.String[][] getParameterInfo()

Overrides:

getParameterInfo in class java.applet.Applet

main

public static void main(java.lang.String[] args)