Question

Use BlueJ java to finish this PolkaDots class, class circle is included below as well.

public class PolkaDots
{
private ArrayList<Circle> dots;// an arrayList field to hold an ArrayList.

/**
* Create a new list of Circles, starts with 5 default circles.
*/
public PolkaDots()
{
dots = new ArrayList<Circle>(); // an arrayList to hold a bunch of circles

Circle circle1 = new Circle(30, 10, 10, "blue");//create the 1st circle
dots.add(circle1);// add the 1st circle to the arrayList   

Circle circle2 = new Circle(10, 50, 50, "red");
dots.add(circle2);

Circle circle3 = new Circle(50, 50, 150, "green");
dots.add(circle3);

Circle circle4 = new Circle(20, 100, 100, "yellow");
dots.add(circle4);

Circle circle5 = new Circle(30, 100, 150, "magenta");
dots.add(circle5);
}

/**
* Create a new list of Circles. Starts with the number of circles
* given by the integer parameter.
*/
//Write another constructor method that accepts a single integer
//parameter "dotNumber" and uses a while loop to add "dotNumber" circles
//to the "dots" ArrayList.
//The added circles should be created with the Circle class's default constructor
//(i.e. they will all be "blue" circles with a diameter of 30 & etc.)

/**
* Adds a new Circle to the "dots" arrayList.
*/
public void addDot(Circle newDot)
{
dots.add(newDot);
}

/**
* Make dots visible.
*/
public void makeVisible()
{
Circle thisDot;
int index = 0;
while(index < dots.size())
{
thisDot = dots.get(index);
thisDot.makeVisible();
index++;
}
}

/**
* Make all dots invisible.
*/
public void makeInvisible()
{
Circle thisDot;
int index = 0;
while(index < dots.size())
{
thisDot = dots.get(index);
thisDot.makeInvisible();
index++;
}
}

public class Circle
{
private int diameter;
   private int xPosition;
   private int yPosition;
   private String color;
   private boolean isVisible;
  
/**
* Create a new circle at default position with default color.
*/
public Circle()
{
       diameter = 30;
       xPosition = 20;
       yPosition = 60;
       color = "blue";
       isVisible = true;
       draw();
}
  
/**
* Create a new circle with given values.
*/
public Circle(int diameter, int xPosition, int yPosition, String color)
{
       this.diameter = diameter;
       this.xPosition = xPosition;
       this.yPosition = yPosition;
       this.color = color;
       isVisible = true;
       draw();
}

   /**
   * 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;
   }
  
   /**
   * Change the position of the circle.
   */
   public void changePosition(int newX, int newY)
   {  
   xPosition = newX;
   yPosition = newY;   
   draw();
}
  
/**
* Change the size to the new size (in pixels). Size must be >= 0.
*/
public void changeSize(int newDiameter)
{
       diameter = newDiameter;
       draw();
}

/**
* Change the color. Valid colors are "red", "yellow", "blue", "green",
   * "magenta" and "black".
*/
public void changeColor(String newColor)
{
       color = newColor;
       draw();
}
  
/**
* Change the color by using a code number.
* Valid colors are "red", "yellow", "blue", "green",
* "magenta" and "black".
*/
public void changeColor(int newColorNumber)
{
if(newColorNumber > 0 && newColorNumber < 7)
{
if(newColorNumber == 1)
{
changeColor("red");
}
else if( newColorNumber == 2)
{
changeColor("yellow");
}
else if( newColorNumber == 3)
{
changeColor("green");
}
else if( newColorNumber == 4)
{
changeColor("blue");
}
else if( newColorNumber == 5)
{
changeColor("magenta");
}
else
{
changeColor("black");
}
}
}
  
   /*
   * 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);
       }
   }
  
/*
* get Diameter
*/
public int getDiameter()
{
return diameter;
}

/*
* get xPosition
*/
public int getXPosition()
{
return xPosition;
}

/*
* get yPosition
*/
public int getYPosition()
{
return yPosition;
}
}

Answer 1

Attached the complete code. If you get any queries, feel free to comment.

Program Screenshot for Indentation Reference:

Program code to copy:

import java.util.*;

public class PolkaDots {
    private ArrayList<Circle> dots;// an arrayList field to hold an ArrayList.

    /**
     * Create a new list of Circles, starts with 5 default circles.
     */
    public PolkaDots() {
        dots = new ArrayList<Circle>(); // an arrayList to hold a bunch of circles

        Circle circle1 = new Circle(30, 10, 10, "blue");// create the 1st circle
        dots.add(circle1);// add the 1st circle to the arrayList

        Circle circle2 = new Circle(10, 50, 50, "red");
        dots.add(circle2);

        Circle circle3 = new Circle(50, 50, 150, "green");
        dots.add(circle3);

        Circle circle4 = new Circle(20, 100, 100, "yellow");
        dots.add(circle4);

        Circle circle5 = new Circle(30, 100, 150, "magenta");
        dots.add(circle5);
    }

    /**
     * Create a new list of Circles. Starts with the number of circles given by the
     * integer parameter.
     */
    // Write another constructor method that accepts a single integer
    // parameter "dotNumber" and uses a while loop to add "dotNumber" circles
    // to the "dots" ArrayList.
    // The added circles should be created with the Circle class's default
    // constructor
    // (i.e. they will all be "blue" circles with a diameter of 30 & etc.)

    public PolkaDots(int dotNumber) {
        // create an empty array list
        dots = new ArrayList<Circle>();
        // add circles
        for (int i = 0; i < dotNumber; i++) {
            dots.add(new Circle());
        }
    }

    /**
     * Adds a new Circle to the "dots" arrayList.
     */
    public void addDot(Circle newDot) {
        dots.add(newDot);
    }

    /**
     * Make dots visible.
     */
    public void makeVisible() {
        Circle thisDot;
        int index = 0;
        while (index < dots.size()) {
            thisDot = dots.get(index);
            thisDot.makeVisible();
            index++;
        }
    }

    /**
     * Make all dots invisible.
     */
    public void makeInvisible() {
        Circle thisDot;
        int index = 0;
        while (index < dots.size()) {
            thisDot = dots.get(index);
            thisDot.makeInvisible();
            index++;
        }
    }

    public void randomizeSizes() {
        // get random class
        Random rand = new Random();

        // loop and set size

        for (Circle c : dots) {
            // 1 and 100 inclusive random number
            c.changeSize(rand.nextInt(100) + 1);
        }
    }

    public void randomizeColors() {
        // get random class
        Random rand = new Random();

        // loop and set color
        for (Circle c : dots) {
            // 1 and 6 inclusive random number
            c.changeSize(rand.nextInt(6) + 1);
        }
    }

    public void randomizePositions() {
        // get random class
        Random rand = new Random();
        // get number of items in dot
        int len = dots.size();
        // loop using while loop
        int i = 0; // current index
        while (i < len) {
            // set the random positions
          
            // OPTIONAL
            // get a random position between 1 and
            // 300 - circle diameter to partial
            // overflow
            int x = rand.nextInt(300 - dots.get(i).getDiameter()) + 1;
            int y = rand.nextInt(300 - dots.get(i).getDiameter()) + 1;
            dots.get(i).changePosition(x, y);
            // increment index
            i++;
        }
    }

}