code: public static Polygon buffer(Geometry geometry,
  			SpatialReference spatialReference, double distance) {
  		double bufferDistance = distance;
  
  		OperatorBuffer op = (OperatorBuffer) factory
  				.getOperator(Operator.Type.Buffer);
  		Geometry result = op.execute(geometry, spatialReference,
  				bufferDistance, null);
  		return (Polygon) result;
  	}
docs: Calculates a buffer polygon of the geometry as specified by the
  distance input. The buffer is implemented in the xy-plane.
  
  See OperatorBuffer
  
  @param geometry Geometry to be buffered.
  @param spatialReference The spatial reference of the geometry.
  @param distance The specified distance for buffer. Same units as the spatial reference.
  @return The buffer polygon at the specified distances.