java - 我的 Vector 丢失数据有什么原因吗？

Question

我当前的目标是将对象添加到 vector 中，以便由我创建的另一个类中的迭代器访问(对于这个项目，我不允许使用 Java 的迭代器)。我的迭代器函数应该返回 vector 内的特定对象。相反，迭代器报告 vector 内的空值。调试后，问题是在启动时添加对象后，对象消失了。将 vector 传递到迭代器类并不能解决问题。我尝试过使用数组列表而不是 vector ，但没有成功。

public void init() { //where im doing the adding
    for (int i = 0; i < 1; i++) {
        cyborg = new Player(ColorUtil.rgb(42, 194, 225), 50, 46.0, baseLocations[0], 40, 100, 100, 0, 50, true);
        go.add((Player) cyborg);
    }

    for (int i = 0; i < 3; i++) {
        NPC = new NPC(ColorUtil.rgb(42, 194, 225), 50, 46.0, baseLocations[0], 40, 100, 100, 0, 50, currStrat);
        go.add((NPC) NPC);
    }

    for (int i = 0; i < 2; i++) {
        drone = new Drone(ColorUtil.rgb(82, 95, 81), r.nextInt(50), 10.0,
                new Point(r.nextFloat() * 1000, r.nextFloat() * 1000), r.nextInt(50));
        go.add(drone);
    }

    for (int i = 0; i < 4; i++) {
        base = new Base(ColorUtil.rgb(169, 235, 0), baseSequence++, baseLocations[i], 10);
        go.add((Fixed) base);
    }

    for (int i = 0; i < 2; i++) {
        eStation = new eStation(ColorUtil.rgb(100, 85, 85), new Point(r.nextFloat() * 1000, r.nextFloat() * 1000),
                r.nextInt(50), 100);
        go.add((Fixed) eStation);

    }



public class GameCollection implements ICollection {

private Vector<GameObject> gameCollection;

public GameCollection() {
    gameCollection = new Vector<GameObject>(); //the vector im having problems with
    System.out.println(gameCollection.toString()); //Test to check if objects in game collection array. Prints null values after startup
}

public IIterator getIterator() {

    GameCollectionIterator gameItr = new GameCollectionIterator(gameCollection);
            return gameItr;


}

public void add(GameObject o) {
    gameCollection.addElement(o);
    //System.out.println(super.toString());
}



public Object elementAt(int location) {
    if(location < gameCollection.size()) {
        return (Object) gameCollection.indexOf(location);
    }

     throw new ArrayIndexOutOfBoundsException(location);

}
public void remove(GameObject o) {
    // TODO Auto-generated method stub
    gameCollection.remove(gameCollection.indexOf(o));
}




private class GameCollectionIterator implements IIterator{
    private int currIndex = 0;

    private Vector <GameObject> game = new Vector <GameObject>();

    public GameCollectionIterator(Vector<GameObject> g) {
        game = g;
    }


    @Override
    public boolean hasNext() {
        if(game.size() <= 0){
            System.out.println("First case");
            return false;

        }
        if(currIndex == game.size() -1){
            System.out.println("Second case");
            return false;
        }
        return true;
    }

    @Override
    public Object getNext() {
        currIndex++;
        return(game.indexOf(currIndex));
    }





    @Override
    public void remove() {
        game.remove(currIndex);
    }

}

Answer 1

我可以在这里看到你的迭代器的一些问题:

@Override
public Object getNext() {
    currIndex++; // (1)
    return(game.indexOf(currIndex)); // (2)
}

1. currIndex++; - 在从 vector 中获取元素之前增加索引，因此基本上总是跳过第一个元素(索引为 0)。

2. game.indexOf(currIndex) - indexOf 返回指定元素第一次出现的索引，请参阅 doc 。您必须使用 get 方法，请参阅 doc .