Question

我有一个名为Game的超级类，它包含一个函数pickPlayers()和一个ArrayList<Player> players，其中包含所选的函数，以及一个扩展它的子类ConsoleGame。问题是当我创建ConsoleGame的实例并调用myInstance.pickPlayers()时，实例的arraylist播放器为空。有任何想法吗？我认为这主要是一个概念性问题，但如果有帮助，这里有一些代码：

这是课程游戏：

import java.util.ArrayList;

public abstract class Game {
    protected String name;
    protected int numPlayers;
    protected ArrayList<Player> players;

    public Game(String n, int np) {
        name = n;
        numPlayers = np;
    }

    protected void pickPlayers(ArrayList<Player> players) {
        /**
         * Choose players at random from the array passed in to play the game
         * Parameters:
         *     ArrayList<Player> players - the array of players
         * Returns:
         *     void
         */
        // choose players at random from players to play the game
        for(int j = 0; j < numPlayers; j++) {
            players.add(players.get(GameNight.generator.nextInt(players.size() - 1)));
        }
    }

    protected abstract void play();
}

这里是BoardGame的子类：

public class BoardGame extends Game {

    /**
     * Luck factor of the game
     */
    private double luckFactor;

    /**
     * Constructor, takes three args to set the instance variables
     * @param n Name of the game
     * @param np Number of players that can play the game at once
     * @param l Luck factor
     */
    public BoardGame(String n, int np, double l) {
        super(n,np);
        luckFactor = l;
    }

    /**
     * Plays the game and chooses a winner.  Winner is chosen to be
     * the person with the largest value of 
     * intelligence + (luck * luckFactor), where luck refer's to the
     * Player's luckiness and luckFactor refers to the Game's instance
     * variable.  This method returns nothing but does call youWin()
     * on the Player that won the game.
     */
    public void play() {
       // code here
    }
}

Answer 1

public void pickPlayers(ArrayList<Player> players) {        
   players.get(..) 
}

它引用了局部变量，你是shadowing你的实例变量。要使用实例属性，您必须使用this进行引用那就是。

this.players.get(..)

注意

顺便提一下，当您创建游戏类型时，players为空。可能是你应该初始化为空列表。

调用函数时java子类状态不变

1 个答案: