Sample Free-Response Solution (A Exam)

(a)

public class CircleFish extends Fish
{
  private boolean justTurned;
  public CircleFish(Environment env, Location loc)
  {
    super(env, loc);
    justTurned = true;
  }

  // other constructors and methods not shown
}


(b)

protected Location nextLocation()
{
  Environment env = environment();
  Location forward = env.getNeighbor(location(), direction());
  Location rightDiag = env.getNeighbor(forward,
                                       direction().toRight());
  if (justTurned && env.isEmpty(forward))
  {
    return forward;
  }
  else if (!justTurned && env.isEmpty(rightDiag))
  {
    return rightDiag;
  }
  else
  {
    return location();
  }
}


(c)

protected void move()
{
  Location oldLoc = location();
  Location nextLoc = nextLocation();

  if (nextLoc.equals(oldLoc))
  {
    changeDirection(direction().toRight());
    justTurned = true;
  }
  else
  {
    changeLocation(nextLoc);

    if (!justTurned)
    {
      changeDirection(direction().toRight());
      justTurned = true;
    }
    else
    {
      justTurned = false;
    }
  }
}