用数组实现矩阵相乘的问题

Question

矩阵相乘有点迷糊
帮忙做下，越简单越好，能实现就OK

设计和编写代表矩阵的Matrix类。该类包括矩阵行列数变量int rows和int cols，矩阵数据数组double data[][]，构造方法Matrix()、Matrix(int rows,int cols)、Matrix(int rows,int cols,double data[][])，获取某元素值的方法getData(int row,int col)，设置某元素值的方法setData(int row,int col,double value)，计算两个矩阵的乘积的方法multiply(Matrix m)以及toString()等内容。

Answer 1

[code="java"]public class Matrix {
int rows;
int cols;
double data[][];

public Matrix() {
    this(0, 0);
}

public Matrix(int rows, int cols) {
    this(rows, cols, new double[rows][cols]);
}

public Matrix(int rows, int cols, double[][] data) {
    super();
    this.rows = rows;
    this.cols = cols;
    this.data = data;
}

public double getData(int row, int col) {
    return data[row][col];
}

public void setData(int row, int col, double value) {
    data[row][col] = value;
}

public double[][] multiply(double[][] m2) {
    int m1rows = data.length;
    int m1cols = data[0].length;
    int m2rows = m2.length;
    int m2cols = m2[0].length;
    if (m1cols != m2rows)
        throw new IllegalArgumentException("matrix doesn't match");
    double[][] result = new double[m1rows][m2cols];

    // multiply
    for (int i = 0; i < m1rows; i++)
        for (int j = 0; j < m2cols; j++)
            for (int k = 0; k < m1cols; k++)
                result[i][j] += data[i][k] * m2[k][j];

    return result;
}

public String toString() {
    StringBuffer sb = new StringBuffer();

    int rows = data.length;
    int cols = data[0].length;

    sb.append("array[" + rows + "][" + cols + "] = " + "\n");
    for (int i = 0; i < rows; i++) {

        for (int j = 0; j < cols; j++)
            sb.append(" " + data[i][j] + " ");
        sb.append("\n");
    }
    sb.append("\n");

    return sb.toString();
}

public static void main(String[] argv) {

    double x[][] = { { 3, 2, 3 }, { 5, 9, 8 }, };
    Matrix m = new Matrix(3, 2, x);

    double y[][] = { { 4, 7 }, { 9, 3 }, { 8, 1 }, };

    double z[][] = m.multiply(y);

    Matrix zm = new Matrix(z.length, z[0].length, z);

    // print result
    System.out.println(zm);
}

}[/code]