更改对象数组中的数据

Question

我一直在尝试为朋友制作游戏，但我无法让我的线路 player[i].setName(getName(pn)); 在课堂 Players 正常工作。我希望能够在列表中设置或更改玩家的姓名。但我一直在这条线上遇到错误。这发生在我将 Player 类中的 public 变量从 static 更改之后。

“线程“主”中的异常 java.lang.NullPointerException 在 worldhomicide.drinkinggame.PlayerInfo.Players.setPlayers(Players.java:16) 在 worldhomicide.drinkinggame.main.Game.main(Game.java:25)"

任何帮助将不胜感激！我在下面发布了所有需要的代码。

游戏类

public class Game{

    public static void main(String[] args) {

        MessageHandler.gameRules(); // Display Game Information
        Players.getAmount();Players.setPlayers();   // Get player data

        System.out.println("What player would you like to look up?");
        int choice = Integer.parseInt(EventHandler.keyboard.next()); choice -= 1;
        System.out.println(Players.player[choice].name);


    }

}

玩家类

public class Players extends EventHandler {

    public static int playerAmount;
    public static Player[] player;

    public static void setPlayers(){    
        player = new Player[playerAmount];

        for(int i = 0; i < player.length; i++){
            int pn = i+1;
            player[i].setName(getName(pn));
        }
    }

    public static void getAmount(){
        MessageHandler.playerAmount();
        playerAmount = Integer.parseInt(keyboard.next());
    }


}

类事件处理程序

public class EventHandler {

    public static Scanner keyboard = new Scanner(System.in);

    public static String getName(int playerNumber){
        System.out.println("What is player " + playerNumber + "'s name?");
        String name = keyboard.next();      
        return name;

    }

}

播放器类

public class Player {

    public String name;
    public int score;

    public void setName(String name){
        this.name = name;
    }

}

Answer 1

请注意，在您的 setPlayers() 方法中，在循环内，您在访问 player[i].setName() 方法之前没有创建 Player 对象。

for(int i = 0; i < player.length; i++){
    int pn = i+1;
    player[i] = new Player(); //you need to create Player object
    player[i].setName(getName(pn));
}