Question

我找到了Java初学者的任务。这是我必须实现的接口。我决定使用HashMap for Players，但现在我注意到我必须返回一个Player数组，对吧？你能帮我理解我怎样才能在getAllPlayers（）方法中做到这一点吗？谢谢

public class LeagueManager implements Manager{
Map<String, Player> players = new HashMap<String, Player>();
public void addPlayer(Player player) {
    players.put(player.getNick(), player);
}

public void removePlayer(Player player) {
    if (!players.isEmpty()) {
        players.remove(player.getNick());
    }
}

public Player getPlayer(String name) {
    if (!players.isEmpty() && players.containsKey(name)) {
        return (Player) players.get(name);
    } else {
        System.out.println("Error: there is no player with nick " + name);
        return null;
    }
}

public Player[] getAllPlayers() {
    if (!players.isEmpty()) {
        return null;
    } else {
        return null;
    }
}


public void addPoints (String name, int points) {
    if (players.containsKey(name)) {
        Player pl = (Player) players.get(name);
        pl.setPoints(points);
    }
}}

Answer 1

您可以使用players.values（）。toArray将值作为数组获取。

@Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        // included to allow fragment to receive onActivityResult

    }

Answer 2

使用以下内容：

public class LeagueManager {
    Map<String, Player> players = new HashMap<String, Player>();
    public void addPlayer(Player player) {
        players.put(player.getNick(), player);
    }

    public void removePlayer(Player player) {
        if (!players.isEmpty()) {
            players.remove(player.getNick());
        }
    }

    public Player getPlayer(String name) {
        if (!players.isEmpty() && players.containsKey(name)) {
            return (Player) players.get(name);
        } else {
            System.out.println("Error: there is no player with nick " + name);
            return null;
        }
    }

    public Player[] getAllPlayers() {
        if (!players.isEmpty()) {
            return players.values().toArray(new Player[players.size()]);
        } else {
            return null;
        }
    }

    public void addPoints (String name, int points) {
        if (players.containsKey(name)) {
            Player pl = (Player) players.get(name);
            pl.setPoints(points);
        }
    }
}

它返回一个与hashMap大小相关的玩家数组。

如何从HashMap获取玩家列表

2 个答案: