How to get the correct Concave Hull using OpenTripPlanner API?

The following code does not give me the result I expected. I expect to have all the points as the nodes of the polygon and the polygon contains all the points. How to use the API correctly? Also if I set thresold less than 1, the program got into some kind infinite loop.import com.vividsolutions.jts.geom.Coordinate;import com.vividsolutions.jts.geom.Geometry;import com.vividsolutions.jts.geom.GeometryCollection;import com.vividsolutions.jts.geom.GeometryFactory;import com.vividsolutions.jts.geom.Point;import java.util.Set;import more