Do you mean something like the following?
Object3D floor = Primitives.getPlane(1, 10f);
Object3D wall1 = Primitives.getPlane(1, 10f);
Object3D wall2 = Primitives.getPlane(1, 10f);
Object3D wall3 = Primitives.getPlane(1, 10f);
Object3D wall4 = Primitives.getPlane(1, 10f);
//NOW ROTATE EACH PLANE INTO POSITION WITH plane.rotate_(float)
wall1.translate(-5f, 0, 0);
wall2.translate(5f, 0, 0);
wall3.translate(0, 0, 5f);
wall4.translate(0, 0, -5f);
world.addObject(floor);
world.addObject(wall1);
world.addObject(wall2);
world.addObject(wall3);
world.addObject(wall4);
world.buildAllObjects();