如何在Java中以不同的方式读取矩阵数组？

import java.util.Scanner;

public class MatrixReader {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        System.out.print("请输入矩阵的行数：");
        int rows = scanner.nextInt();
        System.out.print("请输入矩阵的列数：");
        int cols = scanner.nextInt();

        int[][] matrix = new int[rows][cols];

        System.out.println("请输入矩阵的元素：");
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                matrix[i][j] = scanner.nextInt();
            }
        }

        System.out.println("输入的矩阵为：");
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                System.out.print(matrix[i][j] + " ");
            }
            System.out.println();
        }

        scanner.close();
    }
}

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class MatrixReader {
    public static void main(String[] args) {
        String filePath = "matrix.txt"; // 文件路径

        try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
            String line;
            int rows = 0;
            int cols = 0;

            // 获取矩阵的行数和列数
            while ((line = reader.readLine()) != null) {
                rows++;
                cols = line.split(" ").length;
            }

            int[][] matrix = new int[rows][cols];

            // 重新读取文件，填充矩阵
            reader.close();
            reader = new BufferedReader(new FileReader(filePath));

            int row = 0;
            while ((line = reader.readLine()) != null) {
                String[] elements = line.split(" ");
                for (int col = 0; col < cols; col++) {
                    matrix[row][col] = Integer.parseInt(elements[col]);
                }
                row++;
            }

            System.out.println("读取的矩阵为：");
            for (int i = 0; i < rows; i++) {
                for (int j = 0; j < cols; j++) {
                    System.out.print(matrix[i][j] + " ");
                }
                System.out.println();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import org.apache.commons.math3.linear.MatrixUtils;
import org.apache.commons.math3.linear.RealMatrix;

public class MatrixReader {
    public static void main(String[] args) {
        double[][] array = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};

        RealMatrix matrix = MatrixUtils.createRealMatrix(array);

        System.out.println("读取的矩阵为：");
        for (int i = 0; i < matrix.getRowDimension(); i++) {
            for (int j = 0; j < matrix.getColumnDimension(); j++) {
                System.out.print(matrix.getEntry(i, j) + " ");
            }
            System.out.println();
        }
    }
}