While using one shot, we make the ParticleSystem launch all the particles at once.

In this case, we do not need to add or remove the ParticleSystem to or from the GameEngine, because the onUpdate method of the ParticleSystem does not need to be called (it is only used to emit new particles).

While using one shot, it is only logical to initialize the particle pool with the same number of particles that we plan to use for the shot.

The oneShot method of the ParticleSystem class is as follows:

public void oneShot(GameEngine gameEngine, double x, double y,
    int numParticles) {
  mX = x;
  mY = y;
  mIsEmiting = false;
  for (int i=0; !mParticlePool.isEmpty() && i<numParticles; i++) {
    activateParticle(gameEngine);
  }
}

We set the x and y coordinates from which we will emit and then set isEmitting to false. While updating isEmitting is only necessary when the ParticleSystem is added to the GameEngine, we do it just to be safe. In this case, setting isEmitting to false will...