CODEWITHSUNDEEP
javaarraysdrawing
Josh
Josh

Reputation: 111

drawing random circles, storing their coorindates in an array

This is what I want to accomplish for homework: Design and implement a program that draws circles, with the radius and location of each circle determined at random. If a circle does not overlap with any other circle, draw that circle in black. If a circle overlaps one or more circles, draw it in cyan. Use an array to store a representation of each circle, then determine the color of each circle. Two circles overlap if the distance between their center points is less than the sum of their radii.

I am really close, but I just cannot figure out how to use the sqrt formula in order to compare the radii of the circles that overlap and then to redraw that circle in cyan. I've tried to figure this out in two other posts here: drawing random circles, storing their coorindates in an array and here: draw random circles, first storing the points in an array. I got some pointers, so can anyone give me specific pointers to figure out how to make my for loop use the Math.sqrt function properly in order to compare the radii and then redraw an overlapping circle in cyan? Thank you very much.

UPDATE: I have gotten the Math.sqrt forumla working, but I can't figure out how to structure my for loop in order to only make the circle that overlaps be filled in. I tried to do this using a nested for loop with a boolean in it, but that is making all of the circles fill in. Thank you for your recommendations so far.

Here is the code that I have so far:

 import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JPanel;
import java.awt.*;
import java.awt.event.*;
import java.math.*;

public class RandomCircles extends JPanel
{
    private int[] sizeArray = new int [5];  // radius of each circle
    private int[] xArray = new int [5]; //array to store x coordinates of circles
    private int[] yArray = new int [5]; //array to store y coordinates of circles
    private int x1, x2, y1, y2;
    private boolean overlap = false;


    public RandomCircles()
    {
        Random r = new Random();

        for (int i = 0; i<xArray.length; i++){
            //random numbers from 1 to 20;
            xArray[i] = r.nextInt(200) + 1;
        }
        for (int i = 0; i<yArray.length; i++){
            yArray[i] = r.nextInt(200) + 1;
        }
        for (int i = 0; i<sizeArray.length; i++){
            sizeArray[i] = r.nextInt(100) +1;
        }

        setBackground (Color.blue);
        setPreferredSize (new Dimension(300, 200));
    }
    //  generates all of the circles stored in the array.

    public void paintComponent (Graphics page)
    {
        super.paintComponent(page);
        for (int i = 0 ;i<xArray.length; i++) //this is an iterator that draws the circles and checks for overlapping radii
            for (int j = 0 ;j<xArray.length; j++)
            {
                //boolean overlap = false;
                //is supposed to compare radii of circles to check if they overlap
                {
                    if (Math.sqrt((xArray[i]-xArray[j])*(xArray[i]-xArray[j])+(yArray[i]-yArray[j])*(yArray[i]-yArray[j])) >sizeArray[i]-sizeArray[j]);

                    boolean overlap = true;
                    page.fillOval(xArray[i], yArray[i], sizeArray[i], sizeArray[i]);
                    page.setColor (Color.cyan);
                    repaint();


                } //draws the circles that are stored in the array
                page.drawOval(xArray[i], yArray[i], sizeArray[i], sizeArray[i]);//outer for loop
            }
    }
    public static void main (String[] args)
    {
        JFrame frame = new JFrame ("Circles");
        frame.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);

        frame.getContentPane().add (new RandomCircles());

        frame.pack();
        frame.setVisible(true);
    }
}

Upvotes: 0

Views: 4309

Answers (1)

Jim Lewis
Jim Lewis

Reputation: 45145

//Math.sqrt((x1-x2)*(x1-x2)-(y1-y2)*(y1-y2)), go back and read chapter 7

should be

Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2))

(You need to take the square root of the sum of the squared X and Y distances, not the difference.)

Update:

There are a couple of problems with the overlap detection. Two circles overlap if the sum of their radii is greater than the distance between their centers, but you're taking the difference of the radii and checking if it's less than the distance between the centers.

Also, you should skip the overlap check whenever i == j (since every circle overlaps with itself; you're only interested in overlaps between different circles).

Upvotes: 1

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