HelloJava3Da is extends the Applet class. Some Java 3D programs are written as applications, but
using Applet class gives an easy way to produce a windowed application.
The main class of a Java 3D program typically defines a method to construct the content branch graph.
In the HelloJava3Da example such a method is defined and it is called createSceneGraph().
All steps of the simple recipe are implemented in the constructor of the HelloJava3Da class. Step 1,
create a Canvas3D object, is done on lines 4 through 6. Step 2, create a SimpleUniverse object, is done
on line 13. Step 2a, customize the SimpleUniverse object, is accomplished on line 17. Step 3, construct
content branch, is accomplished by a call to the createSceneGraph() method. Step 4, compile content
branch graph, is done on line 10. Finally, step 5, insert content branch graph into the Locale of the
SimpleUniverse, is completed on line 19.