check my code please?

[Rene Rad]

Hey everyone,

I'm writing a method to shuffle a deck and am unsure if it's executing properly. I'm not sure how to check if it is shuffling 1000 times. (using constant public static final int TIMES_TO_SHUFFLE = 1000) My instructions are in the javadoc before the code. I tried using the debugger but I kept looping in the block and am unsure how to properly use it. Here is my code...

    
import java.util.Random;
import java.util.ArrayList;

public class Deck  
{
   /** The number of times to shuffle */
   public static final int TIMES_TO_SHUFFLE = 1000;  

   private ArrayList<Card> deck;                   // a deck of cards

    /**
     * Constructor for objects of class Deck
     */
    public Deck()
    {
       deck = new ArrayList<Card>();
       loadDeck();
    }

    /**
     * Load a deck with all the cards
     */
    public void loadDeck()
    {
        deck.add(new Card("Ace","Spades",11));
        deck.add(new Card("Ace","Hearts",11));
        deck.add(new Card("Ace","Clubs",11));
        deck.add(new Card("Ace","Diamonds",11));
        deck.add(new Card("King","Spades",10));
        deck.add(new Card("King","Hearts",10));
        deck.add(new Card("King","Clubs",10));
        deck.add(new Card("King","Diamonds",10));
        deck.add(new Card("Queen","Spades",10));
        deck.add(new Card("Queen","Hearts",10));
        deck.add(new Card("Queen","Clubs",10));
        deck.add(new Card("Queen","Diamonds",10));
        deck.add(new Card("Jack","Spades",10));
        deck.add(new Card("Jack","Hearts",10));
        deck.add(new Card("Jack","Clubs",10));
        deck.add(new Card("Jack","Diamonds",10));
        deck.add(new Card("10","Spades",10));
        deck.add(new Card("10","Hearts",10));
        deck.add(new Card("10","Clubs",10));
        deck.add(new Card("10","Diamonds",10));
        deck.add(new Card("9","Spades",9));
        deck.add(new Card("9","Hearts",9));
        deck.add(new Card("9","Clubs",9));
        deck.add(new Card("9","Diamonds",9));
        deck.add(new Card("8","Spades",8));
        deck.add(new Card("8","Hearts",8));
        deck.add(new Card("8","Clubs",8));
        deck.add(new Card("8","Diamonds",8));
        deck.add(new Card("7","Spades",7));
        deck.add(new Card("7","Hearts",7));
        deck.add(new Card("7","Clubs",7));
        deck.add(new Card("7","Diamonds",7));
        deck.add(new Card("6","Spades",6));
        deck.add(new Card("6","Hearts",6));
        deck.add(new Card("6","Clubs",6));
        deck.add(new Card("6","Diamonds",6));
        deck.add(new Card("5","Spades",5));
        deck.add(new Card("5","Hearts",5));
        deck.add(new Card("5","Clubs",5));
        deck.add(new Card("5","Diamonds",5));
        deck.add(new Card("4","Spades",4));
        deck.add(new Card("4","Hearts",4));
        deck.add(new Card("4","Clubs",4));
        deck.add(new Card("4","Diamonds",4));
        deck.add(new Card("3","Spades",3));
        deck.add(new Card("3","Hearts",3));
        deck.add(new Card("3","Clubs",3));
        deck.add(new Card("3","Diamonds",3));
        deck.add(new Card("2","Spades",2));
        deck.add(new Card("2","Hearts",2));
        deck.add(new Card("2","Clubs",2));
        deck.add(new Card("2","Diamonds",2)); 
    }
    
    /**
     * Add a single card to the deck.
     * @param a Card object
     */
    public void addCard(Card cardToAdd)
    {
       deck.add(cardToAdd);
    }
    
    /**
     * Shuffle the deck. This involves selecting random pairs of 
     * cards and swapping them, the number of times to swap determined
     * by the constant TIMES_TO_SHUFFLE. Java provides a shuffle method
     * as part of the Collections interface, however for this assignment
     * you must write your own.
     */
    //public void shuffle()
    
public void shuffle(){
        int i = 0;
        while(i <= TIMES_TO_SHUFFLE) {
            ArrayList copy = new ArrayList();
            for (Object object : deck)
                copy.add(object);
            Random generator = new Random();
            ArrayList result = new ArrayList();
            do{
                int index = (int) (generator.nextDouble() * (double) copy.size());
                result.add(copy.remove(index));
            } while (copy.size() > 0);
            deck = result;
            i++;
        } 
    }
    
    
    
    /**
     * Display the entire contents of the deck. Not used in the
     * game but useful for debugging.
     */
    public void showDeck()
    {
            for (Card x : deck) {
            System.out.println("Type: "+ x.getDescription() + " Suit: " + x.getSuit()+ " Value: " + x.getValue() );
        
        }
    } 
    
    /**
     * Remove the top card (the first card) from the deck.
     * @return the Card object removed or null if there is nothing in the deck.
     */
    public Card takeCard()
    {
        // return card or 
        return null;
    }
    

}

here is the card class.

  
public class Card
{
    // instance variables
    private int value;
    private String suit;
    private String description;

    public Card(String description,
                String suit,
                int value){
                    this.description = description;
                    this.suit = suit;
                    this.value = value;
                }

    public String getDescription(){
        return description;
    }
    
    public String getSuit(){
        return suit;
    }
    
    public int getValue(){
        return value;
    }
    
}

  

[Christophe Verré]

What I can understand from the javadoc is :
1. Take two cards (you need two random indexes)
2. Swap them (no need to use another array)
3. Repeat TIMES_TO_SHUFFLE times

If you follow these simple steps, the method should be easier to write.

[Bert Wilkinson]

It looks like your instructions for the assignment are in the javadoc....

So, with that in mind, your shuffle method looks like it will do some shuffling, but it is not doing what the javadoc says it should. You are looping through the entire deck TIMES_TO_SHUFFLE times vice doing that many "swaps" within the deck. Hopefully that's clear and gives you some direction on where you need to tweak your code.

After you think you are close, you can put a println statement in there to compare the deck before and after a "shuffle" is called to convince yourself something is happening.

[David Newton]

(Consider using loop(s) in loadDeck rather than specifying each card manually, which is rather error-prone.)

Note also that "shuffling" in code is a different operation than shuffling a physical deck of cards--shuffling 1000 times is not likely to give you a deck that's (substantially?) more random than shuffling once.