Collision Detection of two circles - Simple Java Code

Java : Drawing of two circles, mouse motion event handler on one circle, and detect collision with other.

Determining whether or not two circles intersect or overlap or collide is done by comparing the distance between the two circles to the sum of radius of the two circles.


Full working code for collision detection only download here: 


Steps
1)Find the distance between the centers of the two circles(a and b) using the distance formula

 float dxSq = (a.x - b.x) * (a.x - b.x);
 float dySq = (a.y - b.y) * (a.y - b.y);
 int d = (int) Math.sqrt(dxSq + dySq);

2)Then the distance is compared with the radii .

    int r1Pr2 = (int) (a.radius + b.radius);
    if (d < r1Pr2) {
        System.out.println("Collided");
    } else if (d == r1Pr2) {
        System.out.println("Just touching");
    } 

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