Sorry for my mistake 
Here are the links :
http://pastebin.com/96nxsZVZ [HelloWorldOGL.java]
http://pastebin.com/KCxLLmdi [TreeEngine.java]
EDIT :
I am thinking of a thing : Can I simply get axises mesh's point, thus I can set the Object3D.SetCenter() stick the the mesh's point (sorry for bad english).

Here are the links :
http://pastebin.com/96nxsZVZ [HelloWorldOGL.java]
http://pastebin.com/KCxLLmdi [TreeEngine.java]
EDIT :
I am thinking of a thing : Can I simply get axises mesh's point, thus I can set the Object3D.SetCenter() stick the the mesh's point (sorry for bad english).