java在ArrayList中修改ArrayList

Question

我有三节课。玩家等级：

public class Player
{
private String playerName;
private int playerWorth;
private int playerSpent;
// A list of player prize objects.
private ArrayList<Prize> playerPrizeList;

public void Player()
{
     playerPrizeList = new ArrayList <Prize>();
     playerName = "";
     playerWorth = 0;
     playerSpent = 0;
}

public void playerDetails(String playerName, int playerWorth, int playerSpent)
{
    setPlayerName(playerName);
    setPlayerWorth(playerWorth);
    setPlayerSpent(playerSpent);
}

public void prize(String prizeName, int prizeWorth, int prizeCost)
{
    populatePrize(prizeName, prizeWorth, prizeCost);
}

private void populatePrize(String prizeName, int prizeWorth, int prizeCost)
{
    playerPrizeList.add(new Prize(prizeName, prizeWorth, prizeCost));
}

另一个类是PlayerList类，在这个类中，我试图将一个新的player对象添加到一个arrayList中，这个arrayList可以工作，但是在这个player类中，我还有一个prizeList数组（奖品对象）。将播放器添加到ArrayList后，如何检索该对象并更改（我的最后一块代码）。我希望我正确地解释了这一点

public class PlayerList
{
private ArrayList<Player> playerAList; 

public PlayerList() 
{
    playerAList = new ArrayList<Player>();
}

public ArrayList<Player> addPlayer(String playerName, int playerWorth, int playerSpent)
{
    Player newPlayer = new Player();
    newPlayer.setPlayerName(playerName);
    newPlayer.setPlayerWorth(playerWorth);
    newPlayer.setPlayerSpent(playerSpent);
    playerAList.add(newPlayer);
    return playerAList;
}

/**
 * @i is the index of ArrayList for Player Prizes
 */
public void setPlayerPrizeList(int i, String prizeName, int prizeWorth, int prizeCost)
{
    playerAList.get(i) =  currentPlayer;
    currentPlayer.populatePrize(prizeName, prizeWorth, prizeCost);
    playerAList.set(i, currentPlayer);
    return playerAList;
}

Answer 1

总的来说，你的方法看起来不错

但是，您的代码中存在一些问题：

1. 不能为方法调用赋值

   playerAList.get(i) =  currentPlayer;
   

   然而，这应该是可行的：

   currentPlayer = playerAList.get(i);
   

2. 除此之外，您不需要此行：

   playerAList.set(i, currentPlayer);
   

   使用此方法更改的Player将保留在列表中并“自动更新”，因为所有更改都在同一内存块上执行，因此已在其中创建了Player。您的playerAList和currentPlayer都持有对此内存块的引用

3. 还有一件事是错的。不能从返回类型为void的方法中return任何内容：

   return playerAList;
   

---

总之，您的方法setPlayerPrizeList()应该如下所示：

public void setPlayerPrizeList(int i, String prizeName, int prizeWorth, int prizeCost) {
    currentPlayer = playerAList.get(i);
    currentPlayer.populatePrize(prizeName, prizeWorth, prizeCost);
}