Arrays 它一直在说java.lang.NullPointerException。试图弄清楚是什么。有人帮忙吗？

我一直在试图找出代码的错误。有什么我做得不对的吗

公共课2{ 公众卡[]牌组

public void CreateDeck() {
    String[] suit = { "Spades", "Hearts", "Diamonds", "Clubs" };//Array for suit
    int[] number = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 }; // Array for rank

    for (int i = 0; i <suit.length ; i++) {//Looping the suit array
        for (int n = 0; n < number.length; n++) { // Looping the number array
            Card c = new Card(suit[i], number[i]); //Calling the constructor from my card class
            if (deck[i] == null) {
                deck[i] = c;


            }

        }

    }

}

public void displayDeck() {
    for (int i = 0; i <deck.length; i++) {
        if (deck[i] != null) {
            deck[i].display(); // Calling the display method from my card class. 
        }
    }

}

public void CreateDeck（）{
String[]suit={“黑桃”、“红心”、“钻石”、“梅花”}；//suit数组
int[]number={1,2,3,4,5,6,7,8,9,10,11,12,13}；//秩数组
对于（inti=0；i我猜你的牌组是空的

public class deck2 { 

public Card[] deck;  // deck is null

public deck2() {
   deck = new Card[52]; // now it's not.
}

public void CreateDeck() {
    String[] suit = { "Spades", "Hearts", "Diamonds", "Clubs" };//Array for suit
    int[] number = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13 }; // Array for rank

    for (int i = 0; i <suit.length ; i++) {//Looping the suit array
        for (int n = 0; n < number.length; n++) { // Looping the number array
            Card c = new Card(suit[i], number[i]); //Calling the constructor from my card class
            if (deck[i] == null) {
                deck[i] = c;
            }
        }
    }
}

公共类deck2{
公共卡[]牌组；//牌组为空
公众谘询委员会2(){
牌组=新牌[52]；//现在不是了。
}
公共void CreateDeck（）{
String[]suit={“黑桃”、“红心”、“钻石”、“梅花”}；//suit数组
int[]number={1,2,3,4,5,6,7,8,9,10,11,12,13}；//秩数组
对于（int i=0；我调试了吗？发生了什么？在哪里？异常会确切地告诉您它发生在哪一行上。它是哪一行？以及在调试器中设置断点并单步执行代码时会发生什么？