"Class Circle not found in TryBouncingBalls" error message. Help !

Question

Dear People,
I have an error message :
"TryBouncingBalls.java": Error : class Circle not found in class stan_bluej_ch5_p135.TryBouncingBalls at line 67, "
Circle circle = new Circle(xPos + 130, 30);
below are the classes TryBouncingBalls, BouncingBall, BallDemo, Canvas
Thank you in advance
Stan
package stan_bluej_ch5_p135;
import java.awt.*;
import java.awt.geom.*;
public class TryBouncingBalls
public static void main(String[] args)
Canvas myCanvas = new Canvas("Creativity at its best");
myCanvas.setVisible(true);
BouncingBall ball = new BouncingBall(50,50,16, Color.red, 500, myCanvas);
BouncingBall ball2 = new BouncingBall(70,80,20, Color.green, 500, myCanvas);
BouncingBall ball3 = new BouncingBall(90,100,16, Color.red, 500, myCanvas);
BouncingBall ball4 = new BouncingBall(30,30,20, Color.green, 500, myCanvas);
ball.draw();
ball2.draw();
ball.draw();
ball2.draw();
// make them bounce
boolean finished = false;
while(!finished) {
myCanvas.wait(50); // small delay
ball.move();
ball2.move();
ball3.move();
ball4.move();
// stop once ball has travelled a certain distance on x axis
if(ball.getXPosition() >= 550 && ball2.getXPosition() >= 550)
finished = true;
myCanvas.setFont(new Font("helvetica", Font.BOLD, 14));
myCanvas.setForegroundColor(Color.red);
myCanvas.drawString("We are having fun, ...\n\n", 20, 30);
myCanvas.wait(1000);
myCanvas.setForegroundColor(Color.black);
myCanvas.drawString("...drawing lines...", 60, 60);
myCanvas.wait(500);
myCanvas.setForegroundColor(Color.gray);
myCanvas.drawLine(200, 20, 300, 50);
myCanvas.wait(500);
myCanvas.setForegroundColor(Color.blue);
myCanvas.drawLine(220, 100, 370, 40);
myCanvas.wait(500);
myCanvas.setForegroundColor(Color.green);
myCanvas.drawLine(290, 10, 320, 120);
myCanvas.wait(1000);
myCanvas.setForegroundColor(Color.gray);
myCanvas.drawString("...and shapes!", 110, 90);
myCanvas.setForegroundColor(Color.red);
myCanvas.drawString("to bring to focus creative ideas !", 310, 290);
// the shape to draw and move
int xPos = 10;
Rectangle rect = new Rectangle(xPos + 40, 150, 30, 20);
Rectangle rect2 = new Rectangle(xPos + 80, 120, 50, 25);
Rectangle rect3 = new Rectangle(xPos+ 1200, 180, 30, 30);
Rectangle rect4 = new Rectangle(xPos + 150, 220, 40, 15);
myCanvas.fill(rect);
myCanvas.fill(rect2);
myCanvas.fill(rect3);
myCanvas.fill(rect4);
Circle circle = new Circle(xPos + 130, 30);
// Circle circle2 = new Circle(xPos + 150, 50);
// Circle circle3 = new Circle(xPos + 170, 30);
// Circle circle4 = new Circle(xPos + 200, 40);
// myCanvas.fill(circle);
// myCanvas.fill(circle2);
// myCanvas.fill(circle3);
// myCanvas.fill(circle4);
// move the rectangle and circles across the screen
for(int i = 0; i < 200; i ++) {
myCanvas.fill(rect);
myCanvas.fill(rect2);
myCanvas.fill(rect3);
myCanvas.fill(rect4);
myCanvas.wait(10);
myCanvas.erase(rect);
myCanvas.erase(rect2);
myCanvas.erase(rect3);
myCanvas.erase(rect4);
xPos++;
rect.setLocation(xPos, 150);
rect2.setLocation(xPos, 120);
rect3.setLocation(xPos, 180);
rect4.setLocation(xPos, 220);
// at the end of the move, draw once more so that it remains visible
myCanvas.fill(rect);
myCanvas.fill(rect2);
myCanvas.fill(rect3);
myCanvas.fill(rect4);
package stan_bluej_ch5_p135;
import java.awt.*;
import java.awt.geom.*;
* Class BouncingBall - a graphical ball that observes the effect of gravity. The ball
* has the ability to move. Details of movement are determined by the ball itself. It
* will fall downwards, accelerating with time due to the effect of gravity, and bounce
* upward again when hitting the ground.
* This movement can be initiated by repeated calls to the "move" method.
* @author Bruce Quig
* @author Michael Kolling (mik)
* @author David J. Barnes
* @version 1.1 (23-Jan-2002)
public class BouncingBall
private static final int gravity = 3; // effect of gravity
private int ballDegradation = 2;
private Ellipse2D.Double circle;
private Color color;
private int diameter;
private int xPosition;
private int yPosition;
private final int groundPosition; // y position of ground
private Canvas canvas;
private int ySpeed = 1; // initial downward speed
* Constructor for objects of class BouncingBall
* @param xPos the horizontal coordinate of the ball
* @param yPos the vertical coordinate of the ball
* @param ballDiameter the diameter (in pixels) of the ball
* @param ballColor the color of the ball
* @param groundPos the position of the ground (where the wall will bounce)
* @param drawingCanvas the canvas to draw this ball on
public BouncingBall(int xPos, int yPos, int ballDiameter, Color ballColor,
int groundPos, Canvas drawingCanvas)
xPosition = xPos;
yPosition = yPos;
color = ballColor;
diameter = ballDiameter;
groundPosition = groundPos;
canvas = drawingCanvas;
* Draw this ball at its current position onto the canvas.
public void draw()
canvas.setForegroundColor(color);
canvas.fillCircle(xPosition, yPosition, diameter);
* Erase this ball at its current position.
public void erase()
canvas.eraseCircle(xPosition, yPosition, diameter);
* Move this ball according to its position and speed and redraw.
public void move()
// remove from canvas at the current position
erase();
// compute new position
ySpeed += gravity;
yPosition += ySpeed;
xPosition +=2;
// check if it has hit the ground
if(yPosition >= (groundPosition - diameter) && ySpeed > 0) {
yPosition = (int)(groundPosition - diameter);
ySpeed = -ySpeed + ballDegradation;
// draw again at new position
draw();
* return the horizontal position of this ball
public int getXPosition()
return xPosition;
* return the vertical position of this ball
public int getYPosition()
return yPosition;
package stan_bluej_ch5_p135;
import java.awt.*;
import java.awt.geom.*;
* Class BallDemo - provides two short demonstrations showing how to use the
* Canvas class.
* @author Michael Kolling and David J. Barnes
* @version 1.0 (23-Jan-2002)
public class BallDemo
private Canvas myCanvas;
* Create a BallDemo object. Creates a fresh canvas and makes it visible.
public BallDemo()
myCanvas = new Canvas("Ball Demo", 600, 500);
myCanvas.setVisible(true);
* This method demonstrates some of the drawing operations that are
* available on a Canvas object.
public void drawDemo()
myCanvas.setFont(new Font("helvetica", Font.BOLD, 14));
myCanvas.setForegroundColor(Color.red);
myCanvas.drawString("We can draw text, ...", 20, 30);
myCanvas.wait(1000);
myCanvas.setForegroundColor(Color.black);
myCanvas.drawString("...draw lines...", 60, 60);
myCanvas.wait(500);
myCanvas.setForegroundColor(Color.gray);
myCanvas.drawLine(200, 20, 300, 50);
myCanvas.wait(500);
myCanvas.setForegroundColor(Color.blue);
myCanvas.drawLine(220, 100, 370, 40);
myCanvas.wait(500);
myCanvas.setForegroundColor(Color.green);
myCanvas.drawLine(290, 10, 320, 120);
myCanvas.wait(1000);
myCanvas.setForegroundColor(Color.gray);
myCanvas.drawString("...and shapes!", 110, 90);
myCanvas.setForegroundColor(Color.red);
// the shape to draw and move
int xPos = 10;
Rectangle rect = new Rectangle(xPos, 150, 30, 20);
// move the rectangle across the screen
for(int i = 0; i < 200; i ++) {
myCanvas.fill(rect);
myCanvas.wait(10);
myCanvas.erase(rect);
xPos++;
rect.setLocation(xPos, 150);
// at the end of the move, draw once more so that it remains visible
myCanvas.fill(rect);
* Simulates two bouncing balls
public void bounce()
int ground = 400; // position of the ground line
myCanvas.setVisible(true);
// draw the ground
myCanvas.drawLine(50, ground, 550, ground);
// crate and show the balls
BouncingBall ball = new BouncingBall(50, 50, 16, Color.blue, ground, myCanvas);
ball.draw();
BouncingBall ball2 = new BouncingBall(70, 80, 20, Color.red, ground, myCanvas);
ball2.draw();
// make them bounce
boolean finished = false;
while(!finished) {
myCanvas.wait(50); // small delay
ball.move();
ball2.move();
// stop once ball has travelled a certain distance on x axis
if(ball.getXPosition() >= 550 && ball2.getXPosition() >= 550)
finished = true;
ball.erase();
ball2.erase();
package stan_bluej_ch5_p135;
import javax.swing.*;
import java.awt.*;
import java.awt.geom.*;
* Class Canvas - a class to allow for simple graphical
* drawing on a canvas.
* @author Michael Kolling (mik)
* @author Bruce Quig
* @version 1.8 (23.01.2002)
public class Canvas
private JFrame frame;
private CanvasPane canvas;
private Graphics2D graphic;
private Color backgroundColor;
private Image canvasImage;
* Create a Canvas with default height, width and background color
* (300, 300, white).
* @param title title to appear in Canvas Frame
public Canvas(String title)
this(title, 600, 600, Color.white);
* Create a Canvas with default background color (white).
* @param title title to appear in Canvas Frame
* @param width the desired width for the canvas
* @param height the desired height for the canvas
public Canvas(String title, int width, int height)
this(title, width, height, Color.white);
* Create a Canvas.
* @param title title to appear in Canvas Frame
* @param width the desired width for the canvas
* @param height the desired height for the canvas
* @param bgClour the desired background color of the canvas
public Canvas(String title, int width, int height, Color bgColor)
frame = new JFrame();
canvas = new CanvasPane();
frame.setContentPane(canvas);
frame.setTitle(title);
canvas.setPreferredSize(new Dimension(width, height));
backgroundColor = bgColor;
frame.pack();
* Set the canvas visibility and brings canvas to the front of screen
* when made visible. This method can also be used to bring an already
* visible canvas to the front of other windows.
* @param visible boolean value representing the desired visibility of
* the canvas (true or false)
public void setVisible(boolean visible)
if(graphic == null) {
// first time: instantiate the offscreen image and fill it with
// the background color
Dimension size = canvas.getSize();
canvasImage = canvas.createImage(size.width, size.height);
graphic = (Graphics2D)canvasImage.getGraphics();
graphic.setColor(backgroundColor);
graphic.fillRect(0, 0, size.width, size.height);
graphic.setColor(Color.black);
frame.show();
* Provide information on visibility of the Canvas.
* @return true if canvas is visible, false otherwise
public boolean isVisible()
return frame.isVisible();
* Draw the outline of a given shape onto the canvas.
* @param shape the shape object to be drawn on the canvas
public void draw(Shape shape)
graphic.draw(shape);
canvas.repaint();
* Fill the internal dimensions of a given shape with the current
* foreground color of the canvas.
* @param shape the shape object to be filled
public void fill(Shape shape)
graphic.fill(shape);
canvas.repaint();
* Fill the internal dimensions of the given circle with the current
* foreground color of the canvas.
public void fillCircle(int xPos, int yPos, int diameter)
Ellipse2D.Double circle = new Ellipse2D.Double(xPos, yPos, diameter, diameter);
fill(circle);
* Fill the internal dimensions of the given rectangle with the current
* foreground color of the canvas. This is a convenience method. A similar
* effect can be achieved with the "fill" method.
public void fillRectangle(int xPos, int yPos, int width, int height)
fill(new Rectangle(xPos, yPos, width, height));
* Erase the whole canvas.
public void erase()
Color original = graphic.getColor();
graphic.setColor(backgroundColor);
Dimension size = canvas.getSize();
graphic.fill(new Rectangle(0, 0, size.width, size.height));
graphic.setColor(original);
canvas.repaint();
* Erase the internal dimensions of the given circle. This is a
* convenience method. A similar effect can be achieved with
* the "erase" method.
public void eraseCircle(int xPos, int yPos, int diameter)
Ellipse2D.Double circle = new Ellipse2D.Double(xPos, yPos, diameter, diameter);
erase(circle);
* Erase the internal dimensions of the given rectangle. This is a
* convenience method. A similar effect can be achieved with
* the "erase" method.
public void eraseRectangle(int xPos, int yPos, int width, int height)
erase(new Rectangle(xPos, yPos, width, height));
* Erase a given shape's interior on the screen.
* @param shape the shape object to be erased
public void erase(Shape shape)
Color original = graphic.getColor();
graphic.setColor(backgroundColor);
graphic.fill(shape); // erase by filling background color
graphic.setColor(original);
canvas.repaint();
* Erases a given shape's outline on the screen.
* @param shape the shape object to be erased
public void eraseOutline(Shape shape)
Color original = graphic.getColor();
graphic.setColor(backgroundColor);
graphic.draw(shape); // erase by drawing background color
graphic.setColor(original);
canvas.repaint();
* Draws an image onto the canvas.
* @param image the Image object to be displayed
* @param x x co-ordinate for Image placement
* @param y y co-ordinate for Image placement
* @return returns boolean value representing whether the image was
* completely loaded
public boolean drawImage(Image image, int x, int y)
boolean result = graphic.drawImage(image, x, y, null);
canvas.repaint();
return result;
* Draws a String on the Canvas.
* @param text the String to be displayed
* @param x x co-ordinate for text placement
* @param y y co-ordinate for text placement
public void drawString(String text, int x, int y)
graphic.drawString(text, x, y);
canvas.repaint();
* Erases a String on the Canvas.
* @param text the String to be displayed
* @param x x co-ordinate for text placement
* @param y y co-ordinate for text placement
public void eraseString(String text, int x, int y)
Color original = graphic.getColor();
graphic.setColor(backgroundColor);
graphic.drawString(text, x, y);
graphic.setColor(original);
canvas.repaint();
* Draws a line on the Canvas.
* @param x1 x co-ordinate of start of line
* @param y1 y co-ordinate of start of line
* @param x2 x co-ordinate of end of line
* @param y2 y co-ordinate of end of line
public void drawLine(int x1, int y1, int x2, int y2)
graphic.drawLine(x1, y1, x2, y2);
canvas.repaint();
* Sets the foreground color of the Canvas.
* @param newColor the new color for the foreground of the Canvas
public void setForegroundColor(Color blue)
graphic.setColor(Color.blue);
* Returns the current color of the foreground.
* @return the color of the foreground of the Canvas
public Color getForegroundColor()
return graphic.getColor();
* Sets the background color of the Canvas.
* @param newColor the new color for the background of the Canvas
public void setBackgroundColor(Color newColor)
backgroundColor = newColor;
graphic.setBackground(newColor);
* Returns the current color of the background
* @return the color of the background of the Canvas
public Color getBackgroundColor()
return backgroundColor;
* changes the current Font used on the Canvas
* @param newFont new font to be used for String output
public void setFont(Font newFont)
graphic.setFont(newFont);
* Returns the current font of the canvas.
* @return the font currently in use
public Font getFont()
return graphic.getFont();
* Sets the size of the canvas.
* @param width new width
* @param height new height
public void setSize(int width, int height)
canvas.setPreferredSize(new Dimension(width, height));
Image oldImage = canvasImage;
canvasImage = canvas.createImage(width, height);
graphic = (Graphics2D)canvasImage.getGraphics();
graphic.drawImage(oldImage, 0, 0, null);
frame.pack();
* Returns the size of the canvas.
* @return The current dimension of the canvas
public Dimension getSize()
return canvas.getSize();
* Waits for a specified number of milliseconds before finishing.
* This provides an easy way to specify a small delay which can be
* used when producing animations.
* @param milliseconds the number
public void wait(int milliseconds)
try
Thread.sleep(milliseconds);
catch (InterruptedException e)
// ignoring exception at the moment
* Nested class CanvasPane - the actual canvas component contained in the
* Canvas frame. This is essentially a JPanel with added capability to
* refresh the image drawn on it.
private class CanvasPane extends JPanel
public void paint(Graphics g)
g.drawImage(canvasImage, 0, 0, null);

Answer 1

Dear Miciuli,
I found the definition for the circle in the canvas class and used it to creates circles ! Thank you for jaring my brain into thinking !
Stan
Ellipse2D.Double circle = new Ellipse2D.Double(xPos, 70, 30 , 30);