code: public static Maze2D empty(int size) {
          char[][] maze = new char[size][size];
          for (int i = 0; i < size; i++) {
              Arrays.fill(maze[i], Symbol.EMPTY.value());
          }
          maze[0][0] = Symbol.START.value();
          maze[size][size] = Symbol.GOAL.value();
          return new Maze2D(maze);
      }
docs: Generate an empty squared maze of the indicated size.
  @param size maze size.
  @return empty maze.