In this problem, I am using java in BlueJ to finish the TestTwoDimArray class. The Circle class and the Canvas class are complete and do not need to be changed. The instructions on how to complete the TestTwoDimArray class are included in the code, I have attempted the problem and would like to compare my work against a solved model.

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public class Circle { private int diameter; private int xPosition; private int yPosition; private String color; private boolean isVisible; /** * Create a new circle at given position with given diameter and default color. */ public Circle(int diameter, int xPosition, int yPosition, String color) { this.diameter = diameter; this.xPosition = xPosition; this.yPosition = yPosition; this.color = color; isVisible = false; }

/** * Make this circle visible. If it was already visible, do nothing. */ public void makeVisible() { isVisible = true; draw(); } /** * Make this circle invisible. If it was already invisible, do nothing. */ public void makeInvisible() { erase(); isVisible = false; }

/* * Draw the circle with current specifications on screen. */ private void draw() { if(isVisible) { Canvas canvas = Canvas.getCanvas(); canvas.draw(this, color, new Ellipse2D.Double(xPosition, yPosition, diameter, diameter)); canvas.wait(10); } }

/* * Erase the circle on screen. */ private void erase() { if(isVisible) { Canvas canvas = Canvas.getCanvas(); canvas.erase(this); } } }

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public class Canvas { // Note: The implementation of this class (specifically the handling of // shape identity and colors) is slightly more complex than necessary. This // is done on purpose to keep the interface and instance fields of the // shape objects in this project clean and simple for educational purposes.

private static Canvas canvasSingleton;

/** * Factory method to get the canvas singleton object. */ public static Canvas getCanvas() { if(canvasSingleton == null) { canvasSingleton = new Canvas("BlueJ Shapes Demo", 400, 200, Color.white); } canvasSingleton.setVisible(true); return canvasSingleton; }

// ----- instance part -----

private JFrame frame; private CanvasPane canvas; private Graphics2D graphic; private Color backgroundColour; private Image canvasImage; private ArrayList