java编码问题: hangs on a arraylist add

Question

我之前使用 arraylist 作为结构，但在这段代码中它不起作用。由于我找不到错误，有人可以帮助我吗？ (我确信这是我的错误，但 IDE 没有说什么)

流程:首先是类(class)游戏。我调用 runGame 并且它运行正常，直到 Hand hand = new Hand(this.deck); (右侧有一条注释来表明问题

public class Game {

        private ArrayList<Player> playerArray;
    private int maxPlayers;
        private Deck deck;

    //constructor
    public Game(ArrayList playerArray, int maxPlayers)
    {
        this.playerArray = playerArray;
        this.maxPlayers = maxPlayers;
        }

    // game method for the match
    public  void runGame()
        {
            //shuffle of players
            Collections.shuffle(this.playerArray);

            //creation of the deck
            this.deck = new Deck();
            System.out.println(new java.util.Date().toString() +"  "+"deck created");

            //shuffle the deck 
            this.deck.shuffleDeck();
            System.out.println(new java.util.Date().toString() +"  "+"deck shuffled");


            // distribuiting the hands to all players
            //and preventing them to send something
            for (int i = 0; i < this.maxPlayers; i++)
            {
                Player currentPlayer = this.playerArray.get(i);
                Socket socket = currentPlayer.getConnection();

                Hand hand = new Hand(this.deck);// the problem starts here  comes form the constructor of the hand
                 System.out.println(" after hand ");

                sendingBlockString(socket, currentPlayer); //send the block string
                sendingHand(socket, currentPlayer, hand );//send the hand
            }

问题显然出在 Hand 类的 hand 构造函数中，它卡在循环中，exaclty 试图添加甲板上弹出的汽车( Deck.popCard() 函数经过测试并且工作完美，所以它不是阻止 add() 函数)我永远不会到达第二个 system.out.println 这里的代码:

public class Hand  implements Serializable
{

    private ArrayList<Card> theHand;
    private Player player;
    private int handValue ;  // from 1  to 10 


        public Hand(Deck deck)
        {
            for (int i=0; i<4; i++)
            { 
                System.out.println("before popping deck");
                this.theHand.add(i, deck.popCard());// adding the card taken from the deck (5 times)  //// this is the problem  it hangs!
                System.out.println("after add to hand");
            }

         }

Answer 1

你确定它挂起了吗？它应该抛出 NullPointerException，因为您的 ArrayList 尚未初始化。