FastFish Exercise Set 1 Question 6

// Additional method findMoveLocs in Fish class

/** Finds locations to which this fish might move.
 *  A fish may move to any empty adjacent locations except the one
 *  behind it (fish do not move backwards).
 *  @return a list of locations to which this fish might move
 **/
protected ArrayList findMoveLocs()
{
  // Get list of neighboring empty locations.
  ArrayList emptyNbrs = emptyNeighbors();
  Debug.println("Has adjacent empty positions: " + emptyNbrs.toString());

  // Remove the location behind, since fish do not move backwards.
  Direction oppositeDir = direction().reverse();
  Location locationBehind = environment().getNeighbor(location(), oppositeDir);
  emptyNbrs.remove(locationBehind);

  // If no valid empty neighboring locations, then we're done.
  return emptyNbrs;
}

// Modified version of nextLocation method in Fish class

/** Finds this fish's next location.
 *  Finds the possible move locations for this fish and then randomly
 *  chooses one. If this fish cannot move, <code>nextLocation</code>
 *  returns its current location.
 *  @return the next location for this fish
 **/
protected Location nextLocation()
{
  // Get list of possible move locations.
  ArrayList moveLocations = findMoveLocs();
  Debug.print("Possible new locations are: " + moveLocations.toString());

  // If there are no possible moves, then we're done.
  if ( moveLocations.size() == 0 )
    return location();

  // Randomly choose one neighboring empty location and return it.
  Random randNumGen = RandNumGenerator.getInstance();
  int randNum = randNumGen.nextInt(moveLocations.size());
  return (Location) moveLocations.get(randNum);
}