Java generate circle without intersection of existing circles

Question

I have Circle structure :

public class Circle
{
    private int x;
    private int y;
    private int radius;

    private static final int color = Color.WHITE;

    public Circle(int x, int y, int radius)
    {
        this.x = x;
        this.y = y;
        this.radius = radius;
    }

    public int getRadius()
    {
        return radius;
    }

    public int getY()
    {
        return y;
    }

    public int getX()
    {
        return x;
    }

    public int getColor()
    {
        return color;
    }
}

and store them in Stack<Circle>

I want to generate a new circle that have no intersection of other Circles in Stack

Following this answer I do next :

public Circle generateNew(Stack<Circle> circles)
{
    Circle circle = null;
    while (circle == null)
    {
        int x0 = new Random().nextInt(mMaxWidth);
        int y0 = new Random().nextInt(mMaxHeight);
        int R0 = new Random().nextInt(5) * 25;
        boolean isIntersect = !circles.isEmpty();
        for (Circle c : circles)
        {
            int x1 = c.getX();
            int y1 = c.getY();
            int R1 = c.getRadius();
            int d = (x0 - x1) * (x0 - x1) + (y0 - y1) * (y0 - y1);
            if (((R0 - R1) * (R0 - R1) <= d && d <= (R0 + R1) * (R0 + R1)))
            {
                isIntersect = true;
            }
        }
        if (!isIntersect)
        {
            circle = new Circle(x0, y0, R0);
        }
    }
    return circle;
}

But it no working. What i'm doing wrong?

Log after try to generate second Circle :

x0 = 496
y0 = 487
R0 = 100

x1 = 1121
y1 = 188
R1 = 100

What does mean "no working"? It is returing bad values? It throws exception... ? — libik, Apr 16 '15 at 14:59
@libik as you see i do this work in **while** block. When i try to generate second circle - process do infinite work. — Sergey Shustikov, Apr 16 '15 at 15:00
You know that java already has an Ellipse2D class that can model a Circle? — ControlAltDel, Apr 16 '15 at 15:00
how many circles do you have in, when you call it? What is their values? — libik, Apr 16 '15 at 15:02
@libik i have a one circle. see a modified question. i attach some peace of log when i do second generate function. — Sergey Shustikov, Apr 16 '15 at 15:03
isIntersect is always true for a non empty stack of circles. — Pierre Henry, Apr 16 '15 at 15:04
Add a `break;` after `isIntersect = true;`. There is no point comparing with the remaining circles if you already know it is intersecting with one — Code Whisperer, Apr 16 '15 at 15:05

score 6 · Accepted Answer · answered Apr 16 '15 at 15:04

Keep it simple

    boolean isIntersect = false;
    for (Circle c : circles)
    {
        int x1 = c.getX();
        int y1 = c.getY();
        int R1 = c.getRadius();
        int distanceSq = (x0 - x1) * (x0 - x1) + (y0 - y1) * (y0 - y1);
        if (distanceSq <= (R0 + R1) * (R0 + R1))
        {
            isIntersect = true;
            break;
        }

score 1 · Answer 2 · answered Apr 16 '15 at 15:16

More refactoring using @Joop Eggen code:

public Circle generateNew(Stack<Circle> circles)
{
    while (true)
    {
        int x0 = new Random().nextInt(mMaxWidth);
        int y0 = new Random().nextInt(mMaxHeight);
        int R0 = new Random().nextInt(5) * 25;
        boolean isIntersect = false;
        for (Circle c : circles)
        {
            int x1 = c.getX();
            int y1 = c.getY();
            int R1 = c.getRadius();
            int distanceSq = (x0 - x1) * (x0 - x1) + (y0 - y1) * (y0 - y1);
            if (distanceSq <= (R0 + R1) * (R0 + R1))
            {
                isIntersect = true;
                break;
            }
        }
        if (!isIntersect)
        {
            return new Circle(x0, y0, R0); 
        } 
    }
}

I am flattered; mentionable: I edited my answer because of dumb error. — Joop Eggen, Apr 16 '15 at 15:27

Java generate circle without intersection of existing circles

2 Answers2