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From: byhesed <byhesed@gmail.com>
Newsgroups: comp.lang.java.programmer
Subject: Programming question determining two circle's relation
Date: Sat, 30 Apr 2011 01:33:34 -0700 (PDT)
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.programmer:3317

What's wrong with contains and overlaps method in Circle2D class?
It returns incorrect answers.

- A method contains(double x, double y) returns true if the specified
point(x,y) is inside this circle.
- A method contains(Circle2D circle) returns true if the specified
circle is inside this circle.
- A method overlaps(Circle2D circle) return true if the specified
circle overlaps with this circle.

I calculate the distance between two circles:
- double distance = Math.sqrt(Math.pow(circle.x - getX(), 2.0) +
Math.pow(circle.y - getY(), 2.0));

It's wired too me because I think it is not wrong.


// TEST CODE
public class Exercise10_11 {
	public static void main(String[] args) {
		Circle2D c1 = new Circle2D(2, 2, 5.5);
		System.out.println("Area is " + c1.getArea());
		System.out.println("Perimeter is " + c1.getPerimeter());
		System.out.println(c1.contains(3, 3));
		System.out.println(c1.contains(new Circle2D(4, 5, 10.5)));
		System.out.println(c1.overlaps(new Circle2D(3, 5, 2.3)));
	}
}

// Circle2D Class
public class Circle2D {
	private double x;
	private double y;
	private double radius;

	public Circle2D() {
		x = 0;
		y = 0;
		radius = 1;
	}

	public Circle2D(double x, double y, double radius) {
		this.x = x;
		this.y = y;
		this.radius = radius;
	}

	public double getX() {
		return x;
	}

	public double getY() {
		return y;
	}

	public double getArea() {
		return radius * radius * Math.PI;
	}

	public double getPerimeter() {
		return 2 * radius * Math.PI;
	}

	public boolean contains(double x, double y) {
		double distance = Math.pow(getX() - x, 2.0) + Math.pow(getY() - y,
2.0);
		if (distance <= radius)
			return true;
		else
			return false;
	}

	public boolean contains(Circle2D circle) {
		double distance = Math.sqrt(Math.pow(circle.x - getX(), 2.0) +
Math.pow(circle.y - getY(), 2.0));
		if (distance <= Math.abs(radius - circle.radius))
			return true;
		else
			return false;

	}

	public boolean overlaps(Circle2D circle) {
		double distance = Math.sqrt(Math.pow(circle.x - getX(), 2.0) +
Math.pow(circle.y - getY(), 2.0));
		if (distance > Math.abs(radius - circle.radius) && distance <
Math.abs(radius + circle.radius))
			return true;
		else
			return false;
	}
}