java - 尝试使用字段数组作为参数时出现 NullPointerException

Question

这个问题已经有答案了:

What is a NullPointerException, and how do I fix it? (12 个回答)

已关闭 6 年前。

所以我试图测试我的 DeckOfCards 数组是否能够正确打印。这是代码

public class Deck {
    private static final String face[] = {"Ace", "Two", "Three", "Four", "Five", "Six", "Seven", 
                                            "Eight", "Nine", "Ten", "Jack", "Queen", "King"};
    private static final String suit[] = {"Spade", "Club", "Diamond", "Heart"};
    private static final Card deckOfCards[] = new Card [52];

    public Deck(){
        int suitCount = 0;
        int faceCount = 0;
        int faceValue = 0;
        for(int i = 1; i < deckOfCards.length; i++){
            deckOfCards[i].setSuit(suit[suitCount]);
            deckOfCards[i].setFace(face[faceCount], faceValue);
            suitCount++;
            faceCount++;
            faceValue++;
            if(suitCount == 3){
                suitCount = 0;
            }
            if(faceCount == 12){
                faceCount = 0;
            }
            if(faceValue == 13){
                faceValue = 1;
            }
        }
    }

正如你所看到的，我已经在数组中定义了脸部和套装，并且我想将它们分配给正确的值，但是当我尝试运行它时，我在 deckOfCards[i].setSuit(suit[suitCount]); 行收到 nullPointerException

我似乎无法弄清楚为什么它给我这个错误，当我调试它时，它似乎初始化了所有字段，但是当它到达那里时它崩溃了。

Answer 1

您初始化了数组，但没有初始化其中的元素。您可以在循环中执行此操作:

deckOfCards[i] = new Card();
deckOfCards[i].setSuit(suit[suitCount]);