为什么我的卡片不随机？

Question

I created this program in my quest to learn Java but every time I run it I get the same cards over and over again. I can't really find the problem, so why aren't my cards random? I don't really get what I'm missing, is my shuffle method incorrect?

package blackjack;

import java.util.Scanner;

public class BlackJack {

 public static void main(String[] args) {

      System.out.println("Are you ready to play BlackJack?");
      System.out.println();


      playBlackjack();
      System.out.println("Thanks for playing!");


   } 


   static boolean playBlackjack() {

      Deck deck;                  
      Hand dealerHand;   
      Hand playerHand;    

      deck = new Deck();
      dealerHand = new Hand();
      playerHand = new Hand();


      dealerHand.addCard( deck.dealCard() );
      playerHand.addCard( deck.dealCard() ); 
      dealerHand.addCard( deck.dealCard() );
      playerHand.addCard( deck.dealCard() );


      System.out.println();


      if (dealerHand.getBlackjackValue() == 21) {
           System.out.println("The dealer have the " + dealerHand.getCard(0)
                                   + " and the " + dealerHand.getCard(1) + ".");
           System.out.println("You have the " + playerHand.getCard(0)
                                     + " and the " + playerHand.getCard(1) + ".");
           System.out.println();
           System.out.println("The dealer has Blackjack! The dealer wins!");
           return false;
      }

      if (playerHand.getBlackjackValue() == 21) {
           System.out.println("Dealer has the " + dealerHand.getCard(0)
                                   + " and the " + dealerHand.getCard(1) + ".");
           System.out.println("User has the " + playerHand.getCard(0)
                                     + " and the " + playerHand.getCard(1) + ".");
           System.out.println();
           System.out.println("You have Blackjack.  You win.");
           return true;
      }
      while (true) {

           // User decides whether to hit or stand

           System.out.println();
           System.out.println();
           System.out.println("Your cards are:");
           for ( int i = 0; i < playerHand.getCardCount(); i++ )
              System.out.println("    " + playerHand.getCard(i));
           System.out.println("The total of your hand is " +     playerHand.getBlackjackValue());
           System.out.println();
           System.out.println("The dealer is showing the " + dealerHand.getCard(0));
           System.out.println();
           System.out.println("Do you hit(type 0) or stand(type 1)? ");
           Scanner input = new Scanner(System.in);
           int choice = input.nextInt();
              if (choice != 0 && choice != 1){
                 System.out.println("0 or 1 must be inputted to continue ");}
            while (choice != 0 && choice != 1);

           if ( choice == 1 ) {
               break;
           }
           else {
               Card newCard = deck.dealCard();
               playerHand.addCard(newCard);
               System.out.println();
               System.out.println("You hits and your card is the " + newCard);
               System.out.println("The total of the hand is now " + playerHand.getBlackjackValue());
               if (playerHand.getBlackjackValue() > 21) {
                   System.out.println();
                   System.out.println("Fool of a Took! You went over 21 and busted!");
                   return false;  
               }
           }

      }
      //User has stood at this point. Poor fool


      System.out.println();
      System.out.println("You stand. Wouldn't it be nice to sit sometime?");
      System.out.println("The dealer's cards are "+ dealerHand.getCard(0) + " and the " + dealerHand.getCard(1));
      while (dealerHand.getBlackjackValue() <= 16) {
         Card newCard = deck.dealCard();
         System.out.println("The dealer hits and gets the " + newCard);
         dealerHand.addCard(newCard);
         if (dealerHand.getBlackjackValue() > 21) {
            System.out.println();
            System.out.println("The dealer busted! You win!");
            return true;
         }
      }
      System.out.println("The dealer's total is " + dealerHand.getBlackjackValue());
      System.out.println();
      if (playerHand.getBlackjackValue() == dealerHand.getBlackjackValue()) {
         System.out.println("The house always wins on a tie. You lose :(");
         return false;
      }
      else if (dealerHand.getBlackjackValue() >= playerHand.getBlackjackValue()) {
         System.out.println("The dealer wins as he has " + dealerHand.getBlackjackValue() 
                          + " points to your " + playerHand.getBlackjackValue() + "!");
         return false;
      }
      else {
         System.out.println("You win because you had " + playerHand.getBlackjackValue() 
                          + " points while the dealer only had " + dealerHand.getBlackjackValue() + "!");
         return true;
      }

   }
}



package blackjack;

public class Card {

private int suit;
private int rank;
public final static int SPADES = 0,       // Codes for the 4 suits.
                        HEARTS = 1,
                        DIAMONDS = 2,
                        CLUBS = 3;

public final static int ACE = 1,          
                  JACK = 11,            
                  QUEEN = 12,
                  KING = 13;



public Card(int cRank, int cSuit) {
    rank = cRank;
    suit = cSuit;
}

public int getSuit() {
    return suit;
}

public int getRank() {
    return rank;
}

public String getSuitString() {
        // Return a String representing the card's suit.
        // (If the card's suit is invalid, "??" is returned.)
    switch ( suit ) {
       case SPADES:   return "Spades";
       case HEARTS:   return "Hearts";
       case DIAMONDS: return "Diamonds";
       case CLUBS:    return "Clubs";
       default: return "I don't even know";

    }
}

public String getRankString() {
    switch ( rank ) {
       case 1:   return "Ace";
       case 2:   return "2";
       case 3:   return "3";
       case 4:   return "4";
       case 5:   return "5";
       case 6:   return "6";
       case 7:   return "7";
       case 8:   return "8";
       case 9:   return "9";
       case 10:  return "10";
       case 11:  return "Jack";
       case 12:  return "Queen";
       case 13:  return "King";
       default: return "This is impossible!";
    }


}

@Override
public String toString() {
    return getRankString() + " of " + getSuitString();
}


}



package blackjack;

public class Deck {
private Card[] deck;   
private int cardsUsed; 

public Deck() {
   deck = new Card[52];
   int l = 0;
   for ( int suit = 0; suit <= 3; suit++ ) {
      for ( int value = 1; value <= 13; value++ ) {
         deck[l] = new Card(value,suit);
         l++;
      }
   }
   cardsUsed = 0;
}

public void shuffle() {
    for ( int i = 51; i > 0; i-- ) {
        int rand = (int)(Math.random()*(i+1));
        Card temp = deck[i];
        deck[i] = deck[rand];
        deck[rand] = temp;
    }
    cardsUsed = 0;
}

public int cardsLeft() {
    return 52 - cardsUsed;
}

public Card dealCard() {
    if (cardsUsed == 52){
       shuffle();}
    cardsUsed++;
    return deck[cardsUsed - 1];

}
}



package blackjack;

import java.util.*;

public class Hand {

private ArrayList hand; 

public Hand() {
   hand = new ArrayList();
}

public void clear() {
  hand.clear();
}

public void addCard(Card c) {
  if (c != null){
     hand.add(c);
  }
}

public void removeCard(Card c) {
  hand.remove(c);
}

public void removeCard(int location) {
  if (location >= 0 && location < hand.size()){
     hand.remove(location);
  }
   }

public int getCardCount() {
  return hand.size();
}

public Card getCard(int location) {
  if (location >= 0 && location < hand.size()){
     return (Card)hand.get(location);}
  else{
     return null;
  }
 } 
public void sortBySuit() {
  ArrayList newHand = new ArrayList();
  while (hand.size() > 0) {
     int pos = 0; 
     Card c = (Card)hand.get(0); 
     for (int i = 1; i < hand.size(); i++) {
        Card c1 = (Card)hand.get(i);
        if ( c1.getSuit() < c.getSuit() ||
                (c1.getSuit() == c.getSuit() && c1.getRank() < c.getRank()) ) {
            pos = i;
            c = c1;
        }
     }
       Object remove = hand.remove(pos);
     newHand.add(c);
  }
  hand = newHand;
 }


   public int getBlackjackValue() {


     int val;      
     boolean ace;  
     int cards;    

     val = 0;
     ace = false;
     cards = getCardCount();

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

         Card card;     
         int cardVal;  
         card = getCard(i);
         cardVal = card.getRank();  
         if (cardVal > 10) {
             cardVal = 10;   
         }
         if (cardVal == 1) {
             ace = true;     
         }
         val = val + cardVal;
      } 

      if ( ace == true  &&  val + 10 <= 21 ){
          val = val + 10;


      }
      return val;
 }
}

Answer 1

It's impossible to tell because you have not shown us the relevant code. However, if your results are not random, it's probably because Deck.dealCard() is not random.

Update

After reading the new code you posted. You are not shuffling your deck after you create it.

Answer 2

这不是随机的，因为Deck::dealCard()不是随机的。

Answer 3

dealCard is quite strange: when a new Deck is created, cardsUsed is 0, yet you shuffle only if cardsUsed is 52.

public Card dealCard() {
    if (cardsUsed == 52){
       shuffle();}
    cardsUsed++;
    return deck[cardsUsed - 1];

}

I think you should move the call to shuffle to the constructor, right after constructing the deck.