Incorrect sprite graphic is assigned to tiles

I'm now following a series of video tutorials on YouTube, to be specific a Game Programming tutorial by TheChernoProject. I got to episode 36, which is about rendering a level from tiles. I won't get into too much detail on that, but I encountered a strange problem that no one has encountered (at least no one asked for help with it).
To be more precise: I have a Sprite class, a Tile class (with two classes extending it: GrassTile and VoidTile) and a Level class. Level cosists of Tiles, which are made of sprite. You can see the tile here:

public static Tile grass = new GrassTile(Sprite.grass);
public static Tile voidTile = new VoidTile(Sprite.voidSprite);

And the sprite is created like that:

public static Sprite grass = new Sprite(16, 0, 0, Spritesheet.tileset);
public static Sprite voidSprite = new Sprite(16, 0x00AAFF);

Two constructors for sprites: these are

(int size, int x, int y, Spritesheet sheet)
(int size, int colour)

And the level is randomly generated with fields ranging from 0-3 (0 is grass, the rest is currently just VoidTile. But something is wrong with the way it displays graphics. I did check it with the use of printlns, and I'm sure most of it works (it does assign correct Tiles, depending on ID). You can see it there:

ID: 0 |   Tile: com.ekhart.game.level.tile.GrassTile@73d74138 |   Sprite: com.ekhart.game.gfx.Sprite@3d0c51ef
ID: 2 |   Tile: com.ekhart.game.level.tile.VoidTile@3ba0d916 |   Sprite: com.ekhart.game.gfx.Sprite@3d0c51ef
ID: 3 |   Tile: com.ekhart.game.level.tile.VoidTile@3ba0d916 |   Sprite: com.ekhart.game.gfx.Sprite@3d0c51ef
ID: 1 |   Tile: com.ekhart.game.level.tile.VoidTile@3ba0d916 |   Sprite: com.ekhart.game.gfx.Sprite@3d0c51ef

And you might notice, that the Sprite is the same, even though when I create the grass and voidTile classes, they have different sprites assigned to them. And the weird part is that the sprite assigned depends on the order in which I create them. Now all tiles have a voidSprite graphic, because I created VoidTile last. When I swap them around (making GrassTile last), they all have grass sprite. I tried everything I could think of to make this work, but it doesn't. I have uploaded the project folder, so you can import it and check the code, maybe I've missed something.

Project url: https://dl.dropboxusercontent.com/u/18909657/TheGame.rar

Solution

OK, I lied and did look at your rar file, and you are using static inappropriately as I suspected:

public class Tile {

public int x;
public int y;

public static Sprite sprite;

public static Tile grass = new GrassTile(Sprite.grass);
public static Tile voidTile = new VoidTile(Sprite.voidSprite);

public Tile(Sprite sprite) {
    Tile.sprite = sprite;
}

public void render(int x, int y, Screen screen) {
}

public boolean solid() {
    return false;
}

}

By making the sprite field static, it is the now the same for all Tile instances.

Solution:

don't use static inappropriately. The sprite Sprite variable should not be static.
Do post appropriate code on this site so we don't have to do the scut work for you that you should be doing yourself, such as digging for the error.
Don't mix AWT and Swing components unnecessarily.

Note that if your compile complains at you when you change sprite to be non-static, then you must fix the other code that uses the sprite field, not make sprite static again.