Could you please tell me, where can I find the solution for the second exercice in chapter 8 ? Thanks in advance.
The exercises are meant to be there as paths for further learning and exploration, so there aren’t actually any solutions published.
To get something that looks more like the mallet in the picture, you just have to break it down into simple shapes, starting with half a sphere on top, then the cylinder, and so on.
You already have an idea of how to do a cylinder from the code, so you’re just missing the sphere. Here’s a tutorial that shows a simple way of doing a sphere using WebGL: http://learningwebgl.com/blog/?p=1253; you can easily apply the same idea to OpenGL ES on Android.
Hope this helps out! :)