I did some tests, and it does appear that cube primitives do not have any uv texture coordinates on them initially. You could use something like this to apply the texture to your cube:
TextureInfo polyTexture;
int stoneID = TextureManager.getInstance().getTextureID( "stone" );
polyTexture = new TextureInfo( stoneID, 0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 0.0f );
object.getPolygonManager().setPolygonTexture( 0, polyTexture );
object.getPolygonManager().setPolygonTexture( 5, polyTexture );
polyTexture = new TextureInfo( stoneID, 0.5f, 0.5f, 1.0f, 1.0f, 0.0f, 1.0f );
object.getPolygonManager().setPolygonTexture( 1, polyTexture );
object.getPolygonManager().setPolygonTexture( 4, polyTexture );
polyTexture = new TextureInfo( stoneID, 0.0f, 1.0f, 0.0f, 0.0f, 0.5f, 0.5f );
object.getPolygonManager().setPolygonTexture( 2, polyTexture );
object.getPolygonManager().setPolygonTexture( 3, polyTexture );
polyTexture = new TextureInfo( stoneID, 0.5f, 0.5f, 1.0f, 0.0f, 1.0f, 1.0f );
object.getPolygonManager().setPolygonTexture( 6, polyTexture );
object.getPolygonManager().setPolygonTexture( 7, polyTexture );
polyTexture = new TextureInfo( stoneID, 1.0f, 0.0f, 0.0f, 0.0f, 1.0f, 1.0f );
object.getPolygonManager().setPolygonTexture( 8, polyTexture );
object.getPolygonManager().setPolygonTexture( 10, polyTexture );
object.getPolygonManager().setPolygonTexture( 12, polyTexture );
object.getPolygonManager().setPolygonTexture( 14, polyTexture );
polyTexture = new TextureInfo( stoneID, 0.0f, 0.0f, 1.0f, 0.0f, 1.0f, 1.0f );
object.getPolygonManager().setPolygonTexture( 9, polyTexture );
object.getPolygonManager().setPolygonTexture( 11, polyTexture );
object.getPolygonManager().setPolygonTexture( 13, polyTexture );
object.getPolygonManager().setPolygonTexture( 15, polyTexture );
This is not a perfect uv map for the cube - I just guessed on the vertice order for each poly ID. It should get you started, though. I would work on one poly at a time, get the uv coordinates correct for it, then move on to the next poly, and so on.
As you can see, it is generally much easier to just load a model that already has uv coordinates defined - something created in a modeling program, rather than doing it inside your program. Of course if you are creating an object programatically (such as generating a terrain), then you have to manually define the uv coordinates for each polygon.