/**
* Puts this actor into a grid. If there is another actor at the given location, it is removed.
* <br>
* Precondition: (1) This actor is not contained in a grid (2) <code>loc</code> is valid in <code>
* gr</code>
*
* @param gr the grid into which this actor should be placed
* @param loc the location into which the actor should be placed
*/
public void putSelfInGrid(Grid<Actor> gr, Location loc) {
if (grid != null) throw new IllegalStateException("This actor is already contained in a grid.");
Actor actor = gr.get(loc);
if (actor != null) actor.removeSelfFromGrid();
gr.put(loc, this);
grid = gr;
location = loc;
}
/**
* Removes this actor from its grid. <br>
* Precondition: This actor is contained in a grid
*/
public void removeSelfFromGrid() {
if (grid == null) throw new IllegalStateException("This actor is not contained in a grid.");
if (grid.get(location) != this)
throw new IllegalStateException(
"The grid contains a different actor at location " + location + ".");
grid.remove(location);
grid = null;
location = null;
}
/**
* Moves this actor to a new location. If there is another actor at the given location, it is
* removed. <br>
* Precondition: (1) This actor is contained in a grid (2) <code>newLocation</code> is valid in
* the grid of this actor
*
* @param newLocation the new location
*/
public void moveTo(Location newLocation) {
if (grid == null) throw new IllegalStateException("This actor is not in a grid.");
if (grid.get(location) != this)
throw new IllegalStateException(
"The grid contains a different actor at location " + location + ".");
if (!grid.isValid(newLocation))
throw new IllegalArgumentException("Location " + newLocation + " is not valid.");
if (newLocation.equals(location)) return;
grid.remove(location);
Actor other = grid.get(newLocation);
if (other != null) other.removeSelfFromGrid();
location = newLocation;
grid.put(location, this);
}