public class Experiment {
   public static void main (String [] argv) {
      PhysicsElement[] element = new PhysicsElement[3];
      Block b1 = new Block(1e15f, 0f, 0f, 0f);   // f: float
      Block b2 = new Block(1f, 0.10f, 1f, 0f);  // mass, width, position, speed
      Spring spring = new Spring (0.7f, 1f);  // rest length and stiffness
      spring.attachLeftBlock(b1);    // do not change these prototypes
      spring.attachRightBlock(b2);
      b1.attachRightSpring (spring);  
      b2.attachLeftSpring (spring);
      element[0] = b1;
      element[1] = spring;
      element[2] = b2;
      
      Simulator sim = new Simulator (); // do not change this class, 
                                        //Thanks to inheritance code can be reuse. 
      sim.setPhysicsElements(element);
      sim.simulate(0.001f, 20f, 0.1f); // delta time, total time, sampling time.
   } 
}