Question

我是一个相当努力学习Java的人，我在完成我给自己的任务时遇到了一些麻烦。基本上，我正在尝试在page.

结束时进行练习

我成功完成了三节课。 The Card ：

public class Card {

public int nRank; // Used later
public int maxRank = 13; //The max number of Ranks
public int nSuit; // Used later
public int maxSuit = 4; // Max number of suits


//Associate both rank and suit numbers with strings

public String[] ranks = new String[maxRank - 1];
{
    ranks[0] = "two";
    ranks[1] = "three";
    ranks[2] = "four";
    ranks[3] = "five";
    ranks[4] = "six";
    ranks[5] = "seven";
    ranks[6] = "eight";
    ranks[7] = "nine";
    ranks[8] = "ten";
    ranks[9] = "Jack";
    ranks[10] = "Queen";
    ranks[11] = "King";
    ranks[12] = "Ace";

    }

public String[] suits = new String[maxSuit - 1];
{
    suits[0] = "Clubs";
    suits[1] = "Diamonds";
    suits[2] = "Spades";
    suits[3] = "Hearts";
    }

public String suit = suits[nSuit]; //The suit string of the card whose suit number is nSuit
public String rank = ranks[nRank]; //Same but with ranks

//Constructor for the Card object, with two arguments, x for rank, y for suit
public Card(int x,int y){
    this.nRank = x;
    this.nSuit = y;
}

//method to get which card it is in a string
public String whatCard(){
    return rank + " of " + suit;
}
}

The Deck：

    public class Deck {

public static int nRanks = 13; //number of ranks
public static int nSuits = 4; // number of suits
public static int nCard = nRanks * nSuits; // number of cards

Card[] deck = new Card[nCard -1]; //new array called deck to store all the cards 
int h = 0; //a variable to control the place of each card in the array
//constructor for the Deck
public Deck() {

while(h < 52){ // loop until there are 52 cards

// cycles through all the possible combinations between i(ranks) and j(suits) and creates a card with each
for(int i = 1; i <= nRanks; i++){

    for(int j = 1; j <= nSuits; j++){

        deck[h] = new Card(i,j); // creation of the card
        h++; // adds 1 to to h so the program knows how many cards are there
        }
    }

}
}
//method for getting a card depending on its position in the array(x)
    public Card getCard(int x){
    return deck[x-1];   
}
}

卡片/卡片的显示器，我称之为 Shuffle ：

public class Shuffle {

public static void main(String[] args){
        Deck newDeck = new Deck(); // creates a new Deck object
        //loops through all the cards in the deck
    for(int i = 0; i < Deck.nCard; i++){
        System.out.println(newDeck.getCard(i).whatCard()); // prints each card
    }

}

}

虽然eclipse没有注意到代码中的任何错误，但是当我尝试编译时，我会看到：

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 12
    at Card.<init>(Card.java:26)
    at Deck.<init>(Deck.java:20)
    at Shuffle.main(Shuffle.java:5)

我错过了什么？

Answer 1

在你所有长度为N的循环中，你试图从元素1..N中访问。你应该从0 ..（1-N）循环。

例如，如果您有4个套装，则您有一个元素为0,1,2,3的数组。通过说(for j=1; j<=4, j++)，你试图访问超出界限的元素4。

应该阅读(j=0; j<4; j++)。

Answer 2

rank []和suit []的索引从0到12。

你试图从1到13（在for循环中）访问

使用此代码：

for(int i = 0; i < nRanks; i++){

    for(int j = 0; j < nSuits; j++){

        deck[h] = new Card(i,j); // creation of the card
        h++; // adds 1 to to h so the program knows how many cards are there
    }
}

编辑：

我注意到另一个错误，即生成越界的人：在您的Card类中，更改以下行：

public String[] ranks = new String[maxRank - 1];
public String[] suits = new String[maxSuit - 1];

通过

public String[] ranks = new String[maxRank];
public String[] suits = new String[maxSuit];

创建数组时，不指定最后一个索引，而是指定可用的位置。因此，如果您想要输入13个值，请指定新的String [13]。

编辑：完整的甲板课程：

public class Deck {

   public static int nRanks = 13;  
   public static int nSuits = 4; 
   public static int nCard = nRanks * nSuits; 

   Card[] deck = new Card[nCard]; //nCard indexes, not nCard - 1

   public Deck() {
      //remove the while, double loop useless
      for(int i = 0; i < nRanks; i++){
         for(int j = 0; j < nSuits; j++){
            deck[j * nRanks + i] = new Card(i,j);
         }
      }
   }

   public Card getCard(int x){
      return deck[x-1];   
   }
}

Answer 3

Java数组基于零...所以创建一个13 - 1 == 12个元素的新数组，但是数组从零开始意味着访问元素“12”实际上是第13个元素，因此数组超出界限异常。

Answer 4

在卡片中你有：

public int nRank; // Used later
public int maxRank = 13; //The max number of Ranks
public int nSuit; // Used later
public int maxSuit = 4; // Max number of suits

然后是

public String suit = suits[nSuit]; //The suit string of the card whose suit number is nSuit
public String rank = ranks[nRank]; //Same but with ranks

nSuit和nRank没有被初始化为任何理智。尝试设置为0之类的。但是，我不认为这实际上是你想要的，因为套装和等级将在对象构造时设置，而不是你对构造函数的调用。

Answer 5

当您尝试运行它时发生错误（而不是在您尝试编译它时）。这有点挑剔，但最好让术语正确。

问题是你正在尝试使用超出范围的索引获取数组中的元素。在您的数组声明（rank和suit）中，您使用max - 1，而它应该是max。例如，suits[3] = "Hearts"无效，因为suits的长度仅为3（maxSuit -1 = 3）。

一副纸牌

5 个答案: