Java 二维数组乘法错误

Question

我必须为学校编写这个程序，将一对二维数组相乘。当我尝试运行程序时，我不断收到越界：3错误。

我已经多次检查了代码，并且一生都无法弄清楚故障发生在哪里。我运行了一个调试，第一个断点位于 if 语句"if （a[0].length ！= b.length）"，我不知道为什么这是一个断点。

有人可以帮助我吗？

    public class Multiply {
    public static double[][] Multiply_2D_Arrays(double[][] a, double[][] b)
    { 
        if (a[0].length != b.length) // Check to see if the number of a's colums equals the number of b's rows
        {
            throw new IllegalArgumentException("Matrices don't match: " + a[0].length + " != " + b.length);
        }
        int a_rows = a.length;      // Defines the variable M as the row length of array a
        int b_columns = b[0].length;   // Defines the variable N as the column length of array b
        double[][] c = new double[a_rows][b_columns]; // This means that the dimensions of array c will be the rows of a by the columns of b
        for(int i = 0; i < a.length; i++)
            {
                for(int j = 0; j < b[0].length; j++)
                {
                    for(int k = 0; k < a[0].length; )
                    {
                        c[i][j] += a[i][k] * b[k][j];     //Iterates through each row and column of array a and b and then adding it to the dot point sum
                    }
                }
            }
            return c;      //returns the final new array c
        }
    public static void main(String[] args)
    {
        double[][] array1 = {{4.0, 5.0, 6.0}, {2.0, 1.0, 4.0}, {8.0, 7.0, 6.0}, {1.0, 1.0, 2.0}};
        double[][] array2 = {{5.0, 7.0, 7.0, 8.0}, {8.0, 8.0, 9.0, 2.0}, {10.0, 2.0, 3.0, 1.0}};
        double[][] array3 = Multiply.Multiply_2D_Arrays(array1, array2); //Calls the Multiply_2D_Arrays method
        for(int i = 0; i < array3.length; i++)
        {
            for (int j = 0; j < array3.length; j++)
            {
                System.out.print(array3[i][j] + " ");
            }
        }
        System.out.println();
    }
}

Answer 1

你错过了k++ for(int k = 0; k < a[0].length; )

然后你有一个无限循环

另外，如果要将结果打印为矩阵，请将System.out.println()放入 for 循环中：

    for(int i = 0; i < array3.length; i++)
    {
        for (int j = 0; j < array3.length; j++)
        {
            System.out.print(array3[i][j] + " ");
        }
        System.out.println();
    }

Answer 2

如果您将此for(int k = 0; k < a[0].length; )更改为for(int k = 0; k < a[0].length;k++ )错过了 for 循环中的k++，程序将正确执行。