Question

我在编写的包含ArrayList的课程时遇到了问题。代码：

import java.util.ArrayList;


public class AscendingPile {
 public ArrayList<Integer> pile = new ArrayList<Integer>() {{
     add(1);
 }};

public void lay(int card) throws IllegalArgumentException{
    int lastCard = pile.get(pile.size() - 1);
    if(card > lastCard || card == lastCard - 10){
        pile.add(card);
    }
    else {
        throw new IllegalArgumentException("....");
    }
}
// returns last card on the deck
public int getCard() {
    return pile.get(pile.size() - 1);
}

}

问题是lay方法：我没有定义一个新的局部变量，而是希望if语句看起来像这样：

if(card > pile.getCard() || card == pile.getCard() - 10)

但IntelliJ表示无法解析符号getCard（）

如何更改代码以获得所需的结果？

Answer 1

但IntelliJ表示无法解析符号getCard（）

确实如此，ArrayList类没有名为 getCard（）的方法

而不是：

from copy import deepcopy

discarded_overlapped = []
def overlap(overlapped,discarded):
    if all(x is None for x in overlapped):
        discarded.sort()
        if discarded not in discarded_overlapped:
            discarded_overlapped.append(discarded)
        return
    for i in range(len(overlapped)):
        if not overlapped[i] == None:
            overlapped_copy = deepcopy(overlapped)
            discarded_copy = deepcopy(discarded)
            for j in overlapped[i]:
                if j not in discarded:
                    discarded_copy.append(j)
                    overlapped_copy[j] = None
            overlapped_copy[i] = None
            overlap(overlapped_copy,discarded_copy)


Data = [None,[2,3,4],[1],[1],[1,5],[4,6],[5],None,None]
overlap(Data,[])
print(discarded_overlapped)
# [[2, 3, 4, 6], [2, 3, 4, 5], [1, 5], [1, 4, 6]]

直接调用类 AscendingPile

的方法

pile.getCard();

Answer 2

如前所述，只需直接调用getCard（）。

我目前也正在编写纸牌游戏。我强烈建议您使用Stack而不是使用ArrayList作为套牌。（见文件https://docs.oracle.com/javase/7/docs/api/java/util/Stack.html）。

Stack为您提供了有用的方法，如pop（）和push（）。

Pop删除堆栈顶部的对象，就像你现在使用getCard（）方法一样。

无法在Arraylist上调用已定义的方法

2 个答案: