GeometryArray getCoordinate() fail

After obtaining GeometryArray by

GeometryArray ga = (GeometryArray)obj3d.getGeometry();

I would like to obtain a coordinate of this GeometryArray by

Point3f coord = new Point3f();
ga.getCoordinate(0, coord);

However, whenever I traced into the java3d newest source code, namely

GeometryArray.class

I failed to obtain the vertexFormat at this line

int format = ((GeometryArrayRetained)this.retained).vertexFormat;

And then, an exception was thrown out by the following two lines


    if ((format & BY_REFERENCE) != 0)
      throw new IllegalStateException(J3dI18N.getString("GeometryArray82"));

It looks like I can never obtain the object coordinates directly by

getCoordinate()

Can anybody please help?

Cheers
JIA Pei