Java中不允许使用变量声明

Question

这是我的学校项目中的java扑克项目。

开始时，Card类被定义。

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，我试着定义Deck类。但我有一些错误。

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 ; 

    } 


} 

的思想是：首先，我试图创建一个甲板52卡;然后我绑定n次来创建n个套牌。但是，我得到了一些未解决的错误告诉我，

Cannot find symbol i, j.

这是为什么？

Answer 1

因为您在定义i和j之前尝试创建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

对于这一说法

Card card = new Card(j,i); 

存在范围不变量i或j，所以它是你想要将它们移动内环内合法的编译错误

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

大部分的RuntimeError“变量声明在这里是不允许的”是因为缺少大括号。

例子： -

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()); 

    } 
} 

在编译这段代码是给错误：变量声明在这里不允许使用。

但是，

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

这将解决该错误。