Java 中不允许变量声明

Question

这是我学校项目中的一个Java扑克项目。

一开始，定义了卡类。

class Card {
/* constant suits and ranks */
static final String[] Suit = {"Clubs", "Diamonds", "Hearts", "Spades" };
static final String[] Rank = {"","A","2","3","4","5","6","7","8","9","10","J","Q","K"};
/* Data field of a card: rank and suit */
private int cardRank;  /* values: 1-13 (see Rank[] above) */
private int cardSuit;  /* values: 0-3  (see Suit[] above) */
/* Constructor to create a card */
/* throw MyPlayingCardException if rank or suit is invalid */
public Card(int rank, int suit) throws MyPlayingCardException { 
if ((rank < 1) || (rank > 13))
    throw new MyPlayingCardException("Invalid rank:"+rank);
else
        cardRank = rank;
if ((suit < 0) || (suit > 3))
    throw new MyPlayingCardException("Invalid suit:"+suit);
else
        cardSuit = suit;
}
/* Accessor and toString */
/* You may impelemnt equals(), but it will not be used */
public int getRank() { return cardRank; }
public int getSuit() { return cardSuit; }
public String toString() { return Rank[cardRank] + " " + Suit[cardSuit]; }

然后，我尝试定义 Deck 类。但是我有一些错误。

class Decks {
/* this is used to keep track of original n*52 cards */
private List<Card> originalDecks;   
/* this starts with n*52 cards deck from original deck   */
/* it is used to keep track of remaining cards to deal */
/* see reset(): it resets dealDecks to a full deck      */
private List<Card> dealDecks;
/* number of decks in this object */
private int numberDecks;
  public Decks()
{
    ArrayList<Card> originalDecks = new ArrayList<Card>(52);
    ArrayList<Card> dealDecks = new ArrayList<Card>(52); 
     Card card = new Card(j,i);   //Error
    for (int i=0; i<=3; i++)  
        for (int j=0; j<= 13; j++)              
              originalDecks.add(card);   //Error
    dealDecks.addAll(originalDecks); 

}

公共甲板（int n） {

    int numberDecks=n ; 
    Decks originalDecks = new Decks();
    for (int m=0; m< n; m++){
         originalDecks += originalDecks ; 
    }

}

这个想法是：首先，我尝试创建一副有52张牌的牌;然后我绑定它循环n次以创建n副牌。但是，我收到一些未解决的错误，显示我

找不到符号 i、j。

为什么？

Answer 1

因为您尝试在定义i和j之前创建一个Card。另外，请使用大括号。

// Card card = new Card(j,i);
for (int i=0; i<=3; i++) {  
    for (int j=0; j<= 13; j++) {
        Card card = new Card(j,i);
        originalDecks.add(card); 
    }
}

Answer 2

Card card = new Card(j,i);

作用域中没有变量i或j，因此是合法的编译错误

您想将它们移动到内部循环中

 for (int i=0; i<=3; i++)  {
        for (int j=0; j<= 13; j++) {              
            Card card = new Card(j,i);
            originalDecks.add(card); 
        }
  }

Answer 3

主要是运行时错误"这里不允许变量声明"是因为缺少大括号。

例：-

public class Creator
{
    public static void main(String[] args)
    {
        for(int i=0;i<100;i++)
        Creature creature=new Creature(); // Error 
        System.out.println(Creature.numCreated());
    }
}

编译此代码时出现错误：此处不允许变量声明。

但

    for(int i=0;i<100;i++)
    {Creature creature=new Creature();} //no error

这将解决错误。