public static LineString removeRepeatedPoints(final LineString points) {
   final int axisCount = points.getAxisCount();
   final List<Double> coordinates = new ArrayList<>();
   double x = points.getX(0);
   double y = points.getY(0);
   coordinates.add(x);
   coordinates.add(y);
   for (int axisIndex = 2; axisIndex < axisCount; axisIndex++) {
     coordinates.add(points.getCoordinate(0, axisIndex));
   }
   for (int i = 0; i < points.getVertexCount(); i++) {
     final double x1 = points.getX(i);
     final double y1 = points.getY(i);
     if (x != x1 || y != y1) {
       coordinates.add(x1);
       coordinates.add(y1);
       for (int axisIndex = 2; axisIndex < axisCount; axisIndex++) {
         coordinates.add(points.getCoordinate(i, axisIndex));
       }
       x = x1;
       y = y1;
     }
   }
   return new LineStringDouble(axisCount, coordinates);
 }
 public static int orientationIndex(
     final LineString ring, final int index1, final int index2, final int index) {
   return orientationIndex(
       ring.getX(index1),
       ring.getY(index1),
       ring.getX(index2),
       ring.getY(index2),
       ring.getX(index),
       ring.getY(index));
 }
 public static double angleToNext(final LineString points, final int i) {
   final double x1 = points.getX(i);
   final double y1 = points.getY(i);
   double x2;
   double y2;
   int j = i + 1;
   do {
     x2 = points.getX(j);
     y2 = points.getY(j);
     j++;
   } while (x1 == x2 && y1 == y2 && j < points.getVertexCount());
   final double angle = Angle.angle2d(x1, y1, x2, y2);
   return angle;
 }
 public static double angleToPrevious(final LineString points, final int i) {
   if (i > 0) {
     final double x1 = points.getX(i);
     final double y1 = points.getY(i);
     double x2;
     double y2;
     int j = i - 1;
     do {
       x2 = points.getX(j);
       y2 = points.getY(j);
       j--;
     } while (x1 == x2 && y1 == y2 && j > -1);
     final double angle = Angle.angle2d(x1, y1, x2, y2);
     return angle;
   } else {
     throw new IllegalArgumentException("Index must be > 0 to calculate previous angle");
   }
 }
 public static int appendReverse(
     final int axisCount,
     final LineString source,
     final int sourceStartIndex,
     final double[] targetCoordinates,
     final int targetStartIndex,
     final int vertexCount) {
   int coordIndex = targetStartIndex;
   final int sourceVertexCount = source.getVertexCount();
   double previousX;
   double previousY;
   if (targetStartIndex == 0) {
     previousX = Double.NaN;
     previousY = Double.NaN;
   } else {
     previousX = targetCoordinates[(targetStartIndex - 1) * axisCount];
     previousY = targetCoordinates[(targetStartIndex - 1) * axisCount + 1];
   }
   int coordinateIndex = coordIndex * axisCount;
   int sourceIndex = sourceVertexCount - 1 - sourceStartIndex;
   for (int i = 0; i < vertexCount; i++) {
     final double x = source.getX(sourceIndex);
     final double y = source.getY(sourceIndex);
     if (x != previousX || y != previousY) {
       targetCoordinates[coordinateIndex++] = x;
       targetCoordinates[coordinateIndex++] = y;
       for (int axisIndex = 2; axisIndex < axisCount; axisIndex++) {
         final double coordinate = source.getCoordinate(sourceIndex, axisIndex);
         targetCoordinates[coordinateIndex++] = coordinate;
       }
       coordIndex++;
     }
     sourceIndex--;
     previousX = x;
     previousY = y;
   }
   return coordIndex;
 }