public class Image
{
    /*
     * 144 tiles in the example. Hard wire
     * this for now but could make it dynamic.
     */

    public static final int MAX_X = 12;
    public static final int MAX_Y = 12;

    public static final String NO_TILE = "xxxxxxxx";

    public Image ()
    {
        _theWorld = new Tile[MAX_Y][MAX_X];

        for (int i = 0; i < MAX_Y; i++)
        {
            for (int j = 0; j < MAX_X; j++)
            {
                _theWorld[i][j] = null;
            }
        }
    }

    public void addTile (int x, int y, Tile t)
    {
        _theWorld[y][x] = t.removeBorders();
    }

    @Override
    public String toString ()
    {
        String str = null;
        int index = 0;
        int maxIndex = 0;

        do
        {
            for (int i = 0; i < _theWorld.length; i++)
            {
                for (int j = 0; j < _theWorld[0].length; j++)
                {
                    Tile t = _theWorld[i][j];

                    if (t != null)
                    {
                        str += t.line(index);

                        maxIndex = t.numberOfLinex();
                    }
                    else
                        str += NO_TILE;
                }

                str += "\n";
            }

            index++;

        } while (index < maxIndex);

        return str;
    }

    private Tile[][] _theWorld;
}
@@ -273,16 +273,29 @@
  Image (
+boolean debug
 )%0A    %7B%0A
@@ -506,24 +506,49 @@
  %7D%0A        %7D
+%0A%0A        _debug = debug;
 %0A    %7D%0A%0A    
@@ -1418,9 +1418,37 @@
 eWorld;%0A
+    private boolean _debug;%0A
 %7D

Update Image.java