java - 为什么当我递归调用函数时，它返回以前的值而不是新值？

Question

我必须编写一个程序来启动 2 个玩家，并将相同的 Dealer 实例传递给每个玩家。每位玩家发完 7 张牌后，每位玩家将自己的牌列表打印到一个文本文件中，文件名为玩家编号。

现在，在多米诺骨牌游戏中，两个玩家不能拥有相同的牌，即(玩家 1:2,4 和玩家 2:4,2)。

我使用了 boolean 标志的二维数组来控制这一点，但是每当我打印列表时，我发现 2 个或更多玩家具有相同的图 block 。另外，请注意，我必须使用线程来代表玩家。

这是我的 Player 的运行方法。每个玩家应该得到 7 block 。

public synchronized void run() {

try {
    try (PrintWriter writer = new PrintWriter("Player " + player + ".txt")) {
        for (int i = 0; i < 7; i++) {
            Random r = new Random();
            int a = r.nextInt(6);
            int b = r.nextInt(6);
            System.out.println("Player " + player + " is requesting a tile");
            DominoTiles dealt = dealer.deal(a, b);
            tiles[i] = dealt;

            writer.println("Requesting Player " + player + ": ");
            writer.println("Side 1 = " + tiles[i].getSide1() + " Side 2 = " + tiles[i].getSide2());

        }
    } catch (InterruptedException ex) {
        Logger.getLogger(Player.class.getName()).log(Level.SEVERE, null, ex);
    }

} catch (FileNotFoundException ex) {
    Logger.getLogger(Player.class.getName()).log(Level.SEVERE, null, ex);
}

}

这是我的经销商的交易方法。如果函数进入 if block ，我将返回该函数；如果它进入 else if block ，我会再次调用它。问题是，我返回了使函数进入 else if block 的值!

 public synchronized DominoTiles deal(int a, int b) throws FileNotFoundException, InterruptedException {
DominoTiles dealt = new DominoTiles(a, b);
System.out.println("Dealer is dealing");

if ((count < 28 && check[a][b] == false)) {
    System.out.println("Checking " + a + " " + b + ": " + check[a][b]);

    System.out.println(a + " " + b + " has been dealt");

    check[a][b] = true;
    check[b][a] = true;
    System.out.println("Checking now : " + check[a][b]);
    count++;
    System.out.println("Count = " + count);

} else if ((count < 28 && (check[a][b] == true || check[b][a] == true)) || (check[b][a] == true)) {
    System.out.println("I tried to deal the same again!" + a + " " + b + " and it was " + check[a][b] + " " + check[b][a
            ]);
    int c = r.nextInt(7);
    int d = r.nextInt(7);
    deal(c, d);
} else {
    System.out.println("All tiles have been dealt");
    System.exit(0);
}

return dealt;

}

Answer 1

这是因为您没有将递归调用 deal() 的结果分配给 dealt 变量。

修复:

public synchronized DominoTiles deal(int a, int b) throws  FileNotFoundException, InterruptedException {
    DominoTiles dealt = new DominoTiles(a, b);
    System.out.println("Dealer is dealing");

    if ((count < 28 && check[a][b] == false)) {
        System.out.println("Checking " + a + " " + b + ": " + check[a][b]);

        System.out.println(a + " " + b + " has been dealt");

        check[a][b] = true;
        check[b][a] = true;
        System.out.println("Checking now : " + check[a][b]);
        count++;
        System.out.println("Count = " + count);


    } else if ((count < 28 && (check[a][b] == true || check[b][a] == true)) || (check[b][a] == true)) {
        System.out.println("I tried to deal the same again!" + a + " " + b + " and it was " + check[a][b] + " " + check[b][a
        ]);
        int c = r.nextInt(7);
        int d = r.nextInt(7);
        dealt = deal(c, d);
    } else {
        System.out.println("All tiles have been dealt");
        System.exit(0);
    }

    return dealt;

}