[SIS-49] ArrayIndexOutOfBoundsException caused by method getCircularRegionApproximation(int numberOfPoints) in LatLonPointRadius class

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 0.3
• Component/s: Geometry
• Labels: gsoc2012
• Assignee: Ross Laidlaw
• Reporter: Ross Laidlaw
• Created: 05/Jul/12 00:20
• Updated: 17/Nov/17 14:47
• Resolved: 08/Jun/13 04:10

Description

The method public LatLon[] getCircularRegionApproximation(int numberOfPoints) throws an ArrayIndexOutOfBoundsException under certain conditions. This is because of an error in the following loop:

LatLon[] points = new LatLon[numberOfPoints + 1];
for (int i = 0; i < 360; i += (360 / numberOfPoints)) 
{
  points[i] = DistanceUtils.getPointOnGreatCircle(this.center.getLat(),
      this.center.getLon(), radius, i);
}

The exception arises because integer i is used as the array index for the points array, but the value of i jumps up by (360/numberOfPoints) on every iteration of the loop. For example, if numberOfPoints is 10, then i will increase by 36 each time, resulting in the exception. The points array size is set before the loop to 'numberOfPoints + 1'.

As an experiment, I changed the loop as shown below and this appeared to fix the problem. There may be a more elegant solution:

LatLon[] points = new LatLon[numberOfPoints + 1];
for (int i = 0, j = 0; i < 360; i += (360 / numberOfPoints), j++) 
{
  points[j] = DistanceUtils.getPointOnGreatCircle(this.center.getLat(),
      this.center.getLon(), radius, i);
}