How to know what vertex index is picked on a Geometry?

Engines, Libraries and Tools Java 3D
#1

I am trying to get the Texture coordinates which is picked on a geometry but I get stuck to know what vertex index is picked.

pickCanvas.setShapeLocation((MouseEvent) event);
PickResult pickResult = pickCanvas.pickClosest();
Node node = pickResult.getObject();
GeometryArray geoArr = (GeometryArray)((Shape3D)node).getGeometry();
TexCoord2f texCoord = new TexCoord2f();

geoArr.getTextureCoordinate(0, ?, texCoord);

Java doc said:
Class GeometryArray
public void getTextureCoordinate(int texCoordSet, int index, TexCoord3f texCoord)
Gets the texture coordinate associated with the vertex at the specified index in the specified texture coordinate set for this object.
Parameters:
texCoordSet - texture coordinate set in this geometry array
index - source vertex index in this geometry array
texCoord - the vector that will receive the texture coordinates

Thanks in advance.