java - java.lang.NullPointerException 错误尝试填充数组

Question

我试图将二维数组prices[][]中的值（整数）放入数组seatArray[][]中对象的成本变量中。我认为问题在于我试图将价格数组中的值置之不理，因为 seatArray 数组中只有对 null 的对象引用。我将如何解决这个问题？

调用构造函数的行：

        SeatChart seatArray = new SeatChart(givenArray);

构造方法：

public SeatChart(int[][] prices)
{
    Seat[][] seatArray = new Seat[9][10];
    for(int i = 0; i < 9; i++)
    {   
        for(int j = 0; j < 10; j++)
        {
            seatArray[i][j].cost=prices[i][j];
        }
    }
}

Answer 1

Seat[][] seatArray = new Seat[9][10];

这只是声明了数组，并没有用Seat对象初始化数组元素。

for(int i = 0; i < 9; i++)
{   
    for(int j = 0; j < 10; j++)
    {
        // I've used a default Seat() constructor to create the object, in your actual case, it may differ.
        seatArray[i][j] = new Seat(); // Initializing each array element with a new Seat object
        seatArray[i][j].cost=prices[i][j];
    }
}

Answer 2

seatArray[i][j] = new Seat();
seatArray[i][j].cost= prices[i][j];

或者为了清楚起见

Seat seat = new Seat();
seat.setCost(prices[i][j]);
seatArray[i][j] = seat;