java – @ Before / @ BeforeClass似乎不起作用,对象表示null

在开始我想初始化将在测试中使用的对象.
但@BeforeClass并不这样做.

public class InitTests {
private Croupier croupier;
private Player p1,p2;
@BeforeClass
public void setUp() {
    croupier = new Croupier();
    croupier.PlayersInit(5,100);
    p1 = croupier.getPlayer(0);
    p2 = croupier.getPlayer(1);
} @Test // p1,p2,croupier = null,have no idea why.
public void PlayerInitTest() {
    assertEquals(0,p1.getId());
    assertEquals(1,p2.getId());
}}

其他课程：

public class Player {

private ArrayList<Card> hand = new ArrayList<>();
private int coins = 0;
private static int playerNumber = 0;
private int id;
private boolean inGame = true;

public Player(int coins) {
    this.coins = coins;
    id = ++playerNumber;
}

public int addCoins(int amount) {
    coins+=amount;
    return amount;
}

public int substractCoins(int substract) {
    coins-=substract;
    return substract;
}

public int getCoins() {
    return coins;
}

public int getId() {
    return id;
}

public boolean isInGame() {
    return inGame;
}

public void setGameStatus(boolean status) {
    if(getCoins() < 0 )
        inGame = false;
    else 
        inGame = status;
}

public void clearHand() {
    hand.clear();
}}

public class Croupier {

private String name;
private ArrayList<Card> deck = new ArrayList<>();
private ArrayList<Player> allPlayers = new ArrayList<>();
private ArrayList<Player> actual = new ArrayList<>();
private int stack = 0;
private int bigPlayerStack = 0;
private int smallPlayerStack = 0;

public Croupier() {
    System.out.println("tutej.");
}

public Croupier CroupierInit() {
    // static
    PlayersInit(5,100);

    return new Croupier();
}

private void CreateDeck() {
    String[] suits = { "hearts","spades","diamonds","clubs" };

    for (int i = 0; i < suits.length; i++)
        for (int j = 2; j < 15; j++)
            deck.add(new Card(j,suits[i]));

}

private void DeckShuffle() {
    Collections.shuffle(deck);
}

public boolean TurnPlayed() {
    if (!preparedGame())
        return false;

    return true;

}

public void StartGame() {
    preparedGame();
    System.out.println("Game ended.");
}

public boolean preparedGame() {
    clearTable();

    if(!setActualPlayers()) 
        return false;

    setSmallAndBig();
    takeFromSmallAndBig();
    CreateDeck();
    DeckShuffle();

    return true;
}

// set players who are playing
public boolean setActualPlayers() {
    for (Player e : allPlayers)
        if (e.isInGame())
            actual.add(e);

    if (actual.size() < 2)
        return false;

    return true;
}

// take coisn from small and big blind
public void takeFromSmallAndBig() {
    stack += actual.get(bigPlayerStack).substractCoins(20);
    stack += actual.get(smallPlayerStack).substractCoins(10);
}

// set who has small or big blind
public void setSmallAndBig() {
    bigPlayerStack++;
    if (bigPlayerStack > actual.size())
        bigPlayerStack = 0;

    smallPlayerStack = bigPlayerStack - 1;

    if(smallPlayerStack < 0 )
        smallPlayerStack = actual.size() -1;
}

// clear table before game
public void clearTable() {
    actual.clear();
    for (Player e : allPlayers)
        e.clearHand();
}

public void PlayersInit(int numberOfPlayers,int coins) {
    for (int i = 0; i < numberOfPlayers; i++) {
        allPlayers.add(new Player(coins));
    }
}

public Player getPlayer(int index) {
    return allPlayers.get(index);
}}

我确信这些测试是正确的,因为当我在@Test中放入setUp方法(来自该方法的代码)时它才起作用.
我希望这是一个简单的语法问题,作为初学者目前无法设置.

问候.