title: Finding a coordinate in a circle
body: <p>I am doing a mashup using Google Maps under Grails where users can create <a href="http://en.wikipedia.org/wiki/Geofence" rel="nofollow noreferrer">geofences</a> by selecting a point on the map and a radius. This get stored on my database and the application receives constantly a set of coordinates from a GPS device.</p>
  
  <p>I would like to compare the received coordinates with the area stored in the circles. If the point is inside (or outside) the circle the program will fire an action. However, I would like to know how I can find out if the coordinates are located inside/outside the circle. There is a Javascript library which allows doing this but I need to do this on the server.</p>
  
  <p>Is there a Java (or even Groovy) library for this? 
  How would you implement it?</p>