java - 如何从HashMap中获取玩家列表

Question

我找到了一个针对 Java 初学者的任务。这是我必须实现的接口(interface)。我决定对 Players 使用 HashMap，但现在我注意到我必须返回一个 Player 数组，对吗？您能帮我理解如何在 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 获取数组形式的值。

public Player[] getAllPlayers() {
    Player[] result = new Player[players.size()];
    return players.values().toArray(result);
}