我正在尝试将项目添加到卡对象列表中,如果运行此代码,我会得到Nullpointer异常。我相信我不能添加到"零"列表中,但是如何解决此问题?(错误发生在'cards.add(...);')
public class Deck {
private List<Card> cards;
public Deck(String[] ranks, String[] suits, int[] values) {
for (int i = 0; i < ranks.length; i++) {
for (int j = 0; j < suits.length; j++){
cards.add(new Card(ranks[i], suits[j], values[i]));
}
}
}
您需要初始化列表...
private List<Card> cards = new ArrayList<>();
使用指定元素类型初始化列表卡:
private List<Card> cards = new ArrayList<Card>();