import java.util.ArrayList;

public class Deck
{
private final String[] suits = {"Spades", "Hearts", "Clubs", "Diamonds"};
private final String[] faces = {"Ace", "2", "3", "4", "5", "6", "7", "8", "9", "10", "Jack", "Queen", "King"};

private Card[] cards;
private int topCard;

/**
* Construct a deck of cards and initialize the topCard to -1.
*/
public Deck()
{
   topCard = -1;
   cards = new Card[52];
   int j = 0;
   for (int i=0; i<52; i++) {
         cards[i] = new Card(suits[j/13], faces[i-j]);
         if (i == 12 || i == 25 || i == 38) {
            j += 13;
         }
   }
}
/**
* deal() returns the next card or null if the deck is empty.
* @return next Card in the deck.
*/
public Card deal()
{
   topCard++;// set topCard to the next card
   if(topCard < 52)
   {
         return cards[topCard];
   }
   else
   {
         return null;
   }
}

/**
* shuffle() randomly generates a sequence of cards for the card array
*/
public void shuffle()
{
   topCard = -1;// reset the top card
   int nextNumber;
   boolean[] available = new boolean[52];// used to select random #'s between 0 and 51 without replacement

   for(int i = 0; i < 52; i++)
   {
         available[i] = true;//all #'s between 0 and 51 are available
   }

   for(int i = 0; i < 52; i++)
   {
         nextNumber = (int)(Math.random()*52);// select a # from 0 to 51
         while(!available[nextNumber])//while nextNumber is not available (i.e. this number has already been used)
         {
            nextNumber = (int)(Math.random()*52);//try a different number until you find an unused one
         }
         available[nextNumber] = false;// this number is taken
         cards[i] = new Card(suits[nextNumber/13], faces[nextNumber%13

Input Validation Methods Convert the code you used in Asg. 3 for u...