在这基础上加点东西。

public class Matrix {

private int rows; // 行   
private int cols; // 列   
private double[][] data; // 数据   

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

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

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

// 两个矩阵相乘   
public Matrix multiply(Matrix B) {   
    Matrix A = this;   

    if (A.cols != B.rows)
    throw new IllegalArgumentException("矩阵不匹配！");  

    Matrix C = new Matrix(A.rows, B.cols);   
    for (int i = 0; i < C.rows; i++)   
        for (int j = 0; j < C.cols; j++)   
            for (int k = 0; k < A.cols; k++)   
                C.data[i][j] += (A.data[i][k] * B.data[k][j]);   
    return C;   
}   

// 打印矩阵到控制台   
public void show() {   
    for (int i = 0; i < rows; i++) {   
        for (int j = 0; j < cols; j++)   
            System.out.print("     "+data[i][j]);   
        System.out.println();   
    }   
}   
public String toString() {   
  //  return "相乘后的矩阵共有 " + rows + " 行," + cols + "列 ";   
     StringBuffer s = new StringBuffer();   

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

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

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

}

编写MatrixTest类。在该类中通过键盘输入方式确定所要创建的两个矩阵的行列数，根据行列数随机生成数据或键盘输入，并通过setData方法生成矩阵的内容。

这个题目还没打住？？？