Sets class to final, so it cannot be subclassed.
@@ -11,7 +11,7 @@ import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
-public class TileGrid {
+public final class TileGrid {
/** An empty array of tiles. */
private final static AsciiCharacter[] EMPTY_ARRAY = new AsciiCharacter[0];
