BlackJack游戏无法正常运行Java

Question

Here's pretty much my issue in steps. 1. I shuffle my deck and display cards to make sure it shuffled (works perfectly). 2. I play my blackjack game, work perfectly. 3. I shuffle my deck again and display cards again and it doesnt't work. Answers to some questions you guys might ask: 1. The whole program is in a big while loop, the program doesn't end unless i select exit game as an option. 2. I have tried to display my deck again without shuffling it a second time and it works fine.

 public Card deal()
 {
     Card temp;
     temp = storage[top];
     storage[top] = null;
     top++;
     return temp;
 }

 public void shuffle()
 {

int n = storage.length;
for (int i = 0; i < storage.length; i++) 
    {
    // Get a random index of the array past i.
    int random = i + (int) (Math.random() * (n - i));
    // Swap the random element with the present element.
    Card randomElement = storage[random];
    storage[random] = storage[i];
    storage[i] = randomElement;
 }
 }

public void display ()
{
    for (int i = top; i<52; i++)
        storage[i].display();

}

Here is my stack trace Exception in thread "main" java.lang.NullPointerException J of C at blackjack.Deck.display(Deck.java:104) at blackjack.BlackJack.main(BlackJack.java:55) Java Result: 1

case 3:
    {
      myDeck.display();
      break;
    }

and my code from deck.display

public void display ()
{
    for (int i = top; i<storage.length; i++)
        storage[i].display();

}

Answer 1

You never reset your top variable, I think you need to do that. Post your stack trace and the rest of your code, too.