Is it bad practice to use an Enum's ordinal value to index an array in Java?

Question

I have two arrays: Walls and Neighbors.

public boolean[] walls = new boolean[4];
public Cell[] neighbors = new Cell[4];

and I have an Enum:

Answer 1

On a tangential issue, it might be better to use an EnumMap for your neighbours:

Map neighbours = 
    Collections.synchronizedMap(new EnumMap(Dir.class));

neighbours.put(Dir.North, new Cell());

for (Map.Entry neighbour : neighbours.entrySet()) {
    if (neighbour.isVisited()) { ... }
}

etc..

BTW: Enum instances should by convention be all caps,

enum Dir {
    NORTH,
    EAST, 
    SOUTH,
    WEST
}