Java 为什么我只会回来？

当我运行这个程序时，我得到的一切都是空的…我不能再盯着这个看了。我就是找不到错误。。。谁能给我一个提示。。。我不知道还有什么其他相关细节

 public class Deckofcards
   {
      public static final int NCARDS = 52;

      private card[] deckOfCards;         // Contains all 52 cards
      private int currentCard;            // deal THIS card in deck           

      public Deckofcards( )    // Constructor
      {
     deckOfCards = new card[ NCARDS ];

     int i = 0;

     for ( int suit = card.SPADE; suit <= card.DIAMOND; suit++ )
        for ( int rank = 1; rank <= 13; rank++ )
        deckOfCards[i++] = new card(suit, rank);

      private byte cardSuit;
      private byte cardRank;

      public card( int suit, int rank )
      {
     if ( rank == 1 )
        cardRank = 14;     // Give Ace the rank 14
     else
        cardRank = (byte) rank;

     cardSuit = (byte) suit;
      }

      public boolean equals( card x )
      {
     if ( this.cardSuit == x.cardSuit &&
          this.cardRank == x.cardRank    )
        return ( true ); 
     else         
        return ( false );
      }

      public String toString()
      {
     return ( Rank[ cardRank ] + Suit[ cardSuit ] );
      }
   }


    public class Dealer

   {
      public static void main(String[] args)
      {

     Deckofcards a;

     a = new Deckofcards();
     System.out.println(a);      // What a new deck look like     

     System.out.println("Shuffle cards....");            
     a.shuffle(1000);            // Shuffle deck of card "a"
     System.out.println(a);      // Deck after shuffling

     card b;

     b = a.deal();
     System.out.println("Deal a card: " + b);
     b = a.deal();
     System.out.println("Deal a card: " + b);
     b = a.deal();
     System.out.println("Deal a card: " + b);
     b = a.deal();
     System.out.println("Deal a card: " + b);
     b = a.deal();
     System.out.println("Deal a card: " + b);

      }
   }    
     currentCard = 0;
      }

       //shuffle(n): shuffle the deck

      public void shuffle(int n)
      {
     int i, j, k;

     for ( k = 0; k < n; k++ )
     {
         i = (int) ( NCARDS * Math.random() );  // Pick 2 random cards
         j = (int) ( NCARDS * Math.random() );  // in the deck

        //swap these randomly picked cards

         card tmp = deckOfCards[i];
         deckOfCards[i] = deckOfCards[j];
         deckOfCards[j] = tmp;;
     }

     currentCard = 0;   // Reset current card to deal
      }

     //deal(): deal deckOfCards[currentCard] out

      public card deal()
      {
     if ( currentCard < NCARDS )
     {
        return ( deckOfCards[ currentCard++ ] );
     }
     else
     {
        System.out.println("Out of cards error");
        return ( null );  // Error;
     }
      }

      public String toString()
      {
     String s = "";
     int k;

     k = 0;
     for ( int i = 0; i < 4; i++ )
     {
        for ( int j = 1; j <= 13; j++ )
        s += (deckOfCards[k++] + " ");

        s += "\n";
     }
     return ( s );
      }
   }


    public class card
   {
      public static final int SPADE   = 4;
      public static final int HEART   = 3;
      public static final int CLUB    = 2;
      public static final int DIAMOND = 1;

      private static final String[] Suit = { "*", "d", "c", "h", "s"};
      private static final String[] Rank = { "*", "1", "2", "3", "4",
               "5", "6", "7", "8", "9", "10", "J", "Q", "K", "A"};

      private byte cardSuit;
      private byte cardRank;

      public card( int suit, int rank )
      {
     if ( rank == 1 )
        cardRank = 14;     // Give Ace the rank 14
     else
        cardRank = (byte) rank;

     cardSuit = (byte) suit;
      }

      public boolean equals( card x )
      {
     if ( this.cardSuit == x.cardSuit &&
          this.cardRank == x.cardRank    )
        return ( true ); 
     else         
        return ( false );
      }

      public String toString()
      {
     return ( Rank[ cardRank ] + Suit[ cardSuit ] );
      }
   }


    public class Dealer

   {
      public static void main(String[] args)
      {

     Deckofcards a;

     a = new Deckofcards();
     System.out.println(a);      // What a new deck look like     

     System.out.println("Shuffle cards....");            
     a.shuffle(1000);            // Shuffle deck of card "a"
     System.out.println(a);      // Deck after shuffling

     card b;

     b = a.deal();
     System.out.println("Deal a card: " + b);
     b = a.deal();
     System.out.println("Deal a card: " + b);
     b = a.deal();
     System.out.println("Deal a card: " + b);
     b = a.deal();
     System.out.println("Deal a card: " + b);
     b = a.deal();
     System.out.println("Deal a card: " + b);

      }
   }

空空空空空空空空空空空空空空空 空空空空空空空空空空空空空空空 空空空空空空空空空空空空空空空

洗牌。。。。 空空空空空空空空空空空空空空空 空空空空空空空空空空空空空空空 空空空空空空空空空空空空空空空 空空空空空空空空空空空空空空空

发一张卡：空 发一张卡：空 发一张卡：空 发一张卡：空 发卡：空

发现我的错误

在我的cards.java文件中…菱形和黑桃位于错误的位置…下面是更正的部分

for ( int suit = card.DIAMOND; suit <= card.SPADE; suit++ )
        for ( int rank = 1; rank <= 13; rank++ )
        deckOfCards[i++] = new card(suit, rank);

---

for（int suit=card.DIAMOND；suit）所以您希望我们通读200行代码，在某处找到一个
null
。请您的问题包括哪些方法是返回null，请修复您的代码缩进。它们都返回null。我将发布我的结果。我建议您使用Eclipse或IntelliJ之类的调试器逐步检查代码，您可以逐行查看哪些代码返回null，以及在您的执行代码路径中我猜
return（秩[cardRank]+Suit[cardSuit]）；
需要
返回（秩[this.cardRank]+Suit[this.cardSuit]）；
在类卡中，方法为字符串。
for ( int suit = card.DIAMOND; suit <= card.SPADE; suit++ )
        for ( int rank = 1; rank <= 13; rank++ )
        deckOfCards[i++] = new card(suit, rank);