无法初始化Java对象的二维数组 [英] Can't initialize 2D array of objects in Java

问题描述

我试图让一艘战舰游戏，为此我需要的广场，这是一个人可以挑选地点的二维数组。然而，当我运行我的程序，我得到一个空指针异常，当我尝试调用resetBoard（）函数。

战舰类：

 公共类战舰
{
    私人广场[] []正方形;
    私人布尔aircraftCarrierSunk;
    私人布尔battleshipSunk;
    私人布尔submarineSunk;
    私人布尔patrolBoatSunk;
    私人诠释boardSize;
    公众诠释转;    公共战舰（INT X）
    {
        广场=新广场[X] [X]
//的for（int i = 0; I＆LT; boardSize;我++）//不知道我需要这个
// {
//为（INT J = 0; J＆LT; boardSize; J ++）
// {
//广场[I] [J] =新广场（）;
//}
//}
        boardSize = X;
        aircraftCarrierSunk = FALSE;
        battleshipSunk = FALSE;
        submarineSunk = FALSE;
        patrolBoatSunk = FALSE;
    }    公共无效resetBoard（）
    {
        的for（int i = 0; I＆LT; boardSize;我++）
        {
            对于（INT J = 0; J＆LT; boardSize; J ++）
            {
                广场[I] [J] .setContents（0）;
            }
        }
    }
 

驱动：

 公共静态无效的主要（字串[] args）
{
    战舰游戏=新战舰（5）; //在一个5×5板打    的System.out.println（号战列舰！）;
    的System.out.println（----------- \\ n）;    对（INT gameNumber = 1; gameNumber＆下; = 2; gameNumber ++）
    {
        game.resetBoard（）;
 

解决方案

得到它 - 在注释战舰的线条，然后移动 boardSize = X; 上面的for循环

I'm trying to make a battleship game, for which I need a 2D array of squares, which are the places that a person can pick. When I run my program however, I get a null pointer exception when I try to call the resetBoard() function.

Battleship class:

public class Battleship
{
    private Square[][] squares;
    private boolean aircraftCarrierSunk;
    private boolean battleshipSunk;
    private boolean submarineSunk;
    private boolean patrolBoatSunk;
    private int boardSize;
    public int turns;

    public Battleship(int x)
    {
        squares = new Square[x][x];
//         for(int i = 0; i < boardSize; i++) //not sure if I need this
//         {
//             for(int j = 0; j < boardSize; j++)
//             {
//                 squares[i][j] = new Square();
//             }
//         }
        boardSize = x;
        aircraftCarrierSunk = false;
        battleshipSunk = false;
        submarineSunk = false;
        patrolBoatSunk = false;
    }

    public void resetBoard()
    {
        for(int i = 0; i < boardSize; i++)
        {
            for(int j = 0; j < boardSize; j++)
            {
                squares[i][j].setContents(0);
            }
        }
    }

Driver:

public static void main (String [] args)
{
    Battleship game = new Battleship(5);        // play on a 5 by 5 board

    System.out.println("Battleship!");
    System.out.println("-----------\n");

    for (int gameNumber = 1; gameNumber <= 2; gameNumber++)
    {
        game.resetBoard();

解决方案

Got it- uncomment the lines in Battleship, and then move boardSize = x; above that for loop.

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