/**
 * Cell information for the Map.
 */

public class CellId
{
    public static final char ENTRANCE = '@';
    public static final char OPEN_PASSAGE = '.';
    public static final char STONE_WALL = '#';
    
    public static final char FIRST_KEY = 'a';
    public static final char FIRST_DOOR = 'A';
    
    private CellId ()
    {
    }
}
/**
 * Cell information for the Map.
 */

public class CellId
{
    public static final char ENTRANCE = '@';
    public static final char OPEN_PASSAGE = '.';
    public static final char STONE_WALL = '#';
    
    public static final int DOOR_CODE = 32; // a-A

    private CellId ()
    {
    }
}
Update CellId.java