title: Fast circle collision detection
body: <p>I'm trying to write a method that will calculate if two circles are overlapping. I've come up with the following and I'm just curious to know if there is anyway it could be optimised further.</p>
  
  <pre><code>private static boolean isCollision(Point2D p1, float r1, Point2D p2, float r2)
  {
      float a,dx, dy;
      a = (r1+r2) * (r1+r2);
      dx = (float) (p1.getX() - p2.getX());
      dy = (float) (p1.getY() - p2.getY());
  
      if (a &gt; (dx*dx) + (dy*dy))
      {
          return true;
      }
      return false;
  }
  </code></pre>