public static void main(String[] args) {
    HelloTerrainCollision app = new HelloTerrainCollision();
    app.start();
  }
This demo shows a terrain with collision detection, 
that you can walk around in with a first-person perspective.
This code combines HelloCollision and HelloTerrain.
jme3-examples/src/main/java/jme3test/helloworld/HelloTerrainCollision.java