3D APIs under Java environment are compared in this paper. Their difference, as well as related technologies of game engines, are discussed, and some points on object-oriented development are proposed. An interactive 3D navigation system is implemented in a manner different to the scene-diagram of Java3D. Our implementation includes the composition of basic objects, the construction of camera objects, the support for external objects, action objects, and structure of scene-diagram. Moreover, users are allowed to add/delete new objects.