Java，Matrices乘法，如何将值插入矩阵

Question

I am trying to get the matrix multiplication to work, I'm only beginning to learn programming. How can I add values to the 4x4 and 4x4 matrices I created in the main? (This is not my code but I understand most of it, except the use of setElement & getElement if you could please explain to me what it's supposed to do) I would really appreciate the help

public class Matrix{
private float[][] elements;

private int rows;
private int cols;

public int getRows()
{
    return rows;
}

public int getCols()
{
    return cols;
}

public Matrix(int rows, int cols)
{
    this.rows = rows;
    this.cols = cols;
    elements = new float[rows][cols];
}

public void setElement(int row, int col, float value)
{
    elements[row][col] = value;
}

public float getElement(int row, int col)
{
    return elements[row][col];
}

public static Matrix mult(Matrix a, Matrix b)
{
    Matrix c = new Matrix(a.getRows(), b.getCols());

    for (int row = 0; row < a.getRows(); row++)
    {
        for (int col = 0; col < b.getCols(); col++)
        {
            float sum = 0.0f;
            for (int i = 0; i < a.getCols(); i++)
            {
                sum += a.getElement(row, i) * b.getElement(i, col);
            }
            c.setElement(row, col, sum);
        }
    }
    return c;
}

public static void main(String[] args)
{
    Matrix m = new Matrix(4,4);     
    Matrix m1 = new Matrix(4,4);

    Matrix multip = Matrix.mult(m, m1);

    multip = Matrix.mult(m, m1);
    System.out.println(multip);

}

}

Answer 1

The names setElement and getElement pretty much explain themselves. You call setElement on a Matrix to specify a value for the element at a given row-and-column position in that Matrix . And you would call getElement if you wanted to know the value of the element at a given position.

Here's a example of how you'd use them:

Matrix m = new Matrix(2,2); // Make a 2x2 matrix
m.setElement(0, 0, 11.0);   // row #0, col #0 <- 11.0
m.setElement(0, 1, 12.0);   // row #0, col #1 <- 12.0
m.setElement(1, 0, 21.0);   // row #1, col #0 <- 21.0
m.setElement(1, 1, 22.0);   // row #1, col #1 <- 22.0

// This will print "Yes"
if (m.getElement(0, 0) == 11.0)
    System.out.println("Yes");
else 
    System.out.println("No");