java定义一个二维数组，从键盘输入两个矩阵，求两个矩阵的加法、减法、乘积，并输出到屏幕

在Java中，你可以通过定义一个二维数组来存储矩阵数据，然后让用户从键盘输入两个矩阵的元素。对于矩阵运算，如加法、减法和乘法，可以创建相应的函数来处理。下面是一个简单的示例：

import java.util.Scanner;

public class MatrixOperations {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        
        // 定义矩阵大小
        int rows, cols;
        System.out.print("请输入矩阵行数: ");
        rows = scanner.nextInt();
        System.out.print("请输入矩阵列数: ");
        cols = scanner.nextInt();

        // 创建矩阵数组
        double[][] matrixA = new double[rows][cols];
        double[][] matrixB = new double[rows][cols];

        // 输入矩阵A
        System.out.println("请输入矩阵A:");
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                matrixA[i][j] = scanner.nextDouble();
            }
        }

        // 输入矩阵B
        System.out.println("请输入矩阵B:");
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                matrixB[i][j] = scanner.nextDouble();
            }
        }

        // 矩阵操作
        double[][] sum = addMatrices(matrixA, matrixB);
        double[][] difference = subtractMatrices(matrixA, matrixB);
        double[][] product = multiplyMatrices(matrixA, matrixB);

        // 输出结果
        System.out.println("\n矩阵A + B:");
        printMatrix(sum);
        System.out.println("\n矩阵A - B:");
        printMatrix(difference);
        System.out.println("\n矩阵A * B:");
        printMatrix(product);
    }

    // 加法函数
    public static double[][] addMatrices(double[][] a, double[][] b) {
        return new double[a.length][a[0].length] {
            @Override
            public double get(int row, int col) {
                return a[row][col] + b[row][col];
            }
        };
    }

    // 减法函数
    public static double[][] subtractMatrices(double[][] a, double[][] b) {
        return new double[a.length][a[0].length] {
            @Override
            public double get(int row, int col) {
                return a[row][col] - b[row][col];
            }
        };
    }

    // 乘法函数，这里假设两个矩阵相乘后的结果也是同维度
    public static double[][] multiplyMatrices(double[][] a, double[][] b) {
        double[][] result = new double[a.length][b[0].length];
        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; k++) {
                    result[i][j] += a[i][k] * b[k][j];
                }
            }
        }
        return result;
    }

    // 打印矩阵
    private static void printMatrix(double[][] matrix) {
        for (double[] row : matrix) {
            for (double value : row) {
                System.out.print(value + " ");
            }
            System.out.println();
        }
    }
}