This Java3D application renders a single ColorCube that rotates when any key is pressed.

 import java.applet.Applet;
import java.awt.BorderLayout;
import java.awt.Frame;
import java.awt.event.KeyEvent;
import java.util.Enumeration;

import javax.media.j3d.Behavior;
import javax.media.j3d.BoundingSphere;
import javax.media.j3d.BranchGroup;
import javax.media.j3d.Canvas3D;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.media.j3d.WakeupOnAWTEvent;

import com.sun.j3d.utils.applet.MainFrame;
import com.sun.j3d.utils.geometry.ColorCube;
import com.sun.j3d.utils.universe.SimpleUniverse;

//   SimpleBehaviorApp renders a single ColorCube
//   that rotates when any key is pressed.

public class SimpleBehaviorApp extends Applet {

  public class SimpleBehavior extends Behavior {

    private TransformGroup targetTG;

    private Transform3D rotation = new Transform3D();

    private double angle = 0.0;

    // create SimpleBehavior
    SimpleBehavior(TransformGroup targetTG) {
      this.targetTG = targetTG;
    }

    // initialize the Behavior
    //     set initial wakeup condition
    //     called when behavior beacomes live
    public void initialize() {
      // set initial wakeup condition
      this.wakeupOn(new WakeupOnAWTEvent(KeyEvent.KEY_PRESSED));
    }

    // behave
    // called by Java 3D when appropriate stimulus occures
    public void processStimulus(Enumeration criteria) {
      // decode event

      // do what is necessary
      angle += 0.1;
      rotation.rotY(angle);
      targetTG.setTransform(rotation);
      this.wakeupOn(new WakeupOnAWTEvent(KeyEvent.KEY_PRESSED));
    }

  } // end of class SimpleBehavior

  public BranchGroup createSceneGraph() {
    // Create the root of the branch graph
    BranchGroup objRoot = new BranchGroup();

    TransformGroup objRotate = new TransformGroup();
    objRotate.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);

    objRoot.addChild(objRotate);
    objRotate.addChild(new ColorCube(0.4));

    SimpleBehavior myRotationBehavior = new SimpleBehavior(objRotate);
    myRotationBehavior.setSchedulingBounds(new BoundingSphere());
    objRoot.addChild(myRotationBehavior);

    // Let Java 3D perform optimizations on this scene graph.
    objRoot.compile();

    return objRoot;
  } // end of CreateSceneGraph method of SimpleBehaviorApp

  // Create a simple scene and attach it to the virtual universe

  public SimpleBehaviorApp() {
    setLayout(new BorderLayout());
    Canvas3D canvas3D = new Canvas3D(null);
    add("Center", canvas3D);

    BranchGroup scene = createSceneGraph();

    // SimpleUniverse is a Convenience Utility class
    SimpleUniverse simpleU = new SimpleUniverse(canvas3D);

    // This will move the ViewPlatform back a bit so the
    // objects in the scene can be viewed.
    simpleU.getViewingPlatform().setNominalViewingTransform();

    simpleU.addBranchGraph(scene);
  } // end of SimpleBehaviorApp (constructor)

  //  The following allows this to be run as an application
  //  as well as an applet

  public static void main(String[] args) {
    System.out
        .print("SimpleBehaviorApp.java \n- a demonstration of creating a simple");
    System.out
        .println("behavior class to provide interaction in a Java 3D scene.");
    System.out
        .println("When the app loads, press any key to make the cube rotate.");
    System.out
        .println("This is a simple example progam from The Java 3D API Tutorial.");
    System.out.println("The Java 3D Tutorial is available on the web at:");
    System.out.println("http://www.sun.com/desktop/java3d/collateral");
    Frame frame = new MainFrame(new SimpleBehaviorApp(), 256, 256);
  } // end of main (method of SimpleBehaviorApp)

} // end of class SimpleBehaviorApp