Changing the view is done like that :

ViewingPlatform platform = universe.getViewingPlatform();
TransformGroup platformTransformGroup =
platform.getViewPlatformTransform();
Transform3D camera = new Transform3D();
platformTransformGroup.getTransform(camera);
Point3d cameraPosition = new Point3d(-0.2, 1.5, 2.5);
camera.lookAt(cameraPosition, new Point3d(1, 0, 0), new Vector3d(0, 5,
0));
camera.invert();
platformTransformGroup.setTransform(camera);

JAVADOC FOR LOOKAT :
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

lookAt

public void lookAt(Point3d eye,
                  Point3d center,
                  Vector3d up)

   Helping function that specifies the position and orientation of a
view matrix. The inverse of this transform can be used to control the
ViewPlatform object within the scene graph.

   Parameters:
       eye - the location of the eye
       center - a point in the virtual world where the eye is looking
       up - an up vector specifying the frustum's up direction