I think you don't need JavaObject.
Try something like this:
Dim Cam As Camera2
Dim l As List
l.Initialize
Cam.Initialize("Camera")
l = Cam.GetSupportedPreviewSizes(0)
Log(l)
(ArrayList) [4128x3096, 4128x2322, 3264x2448, 3264x1836, 3088x3088, 2048x1536, 2048x1152, 1920x1080, 1280x720, 960x720, 720x480, 640x480, 352x288, 320x240, 256x144, 176x144]