Implementation of Matrix multiplication in java

              Matrix is one of the fundamental concepts in java. A matrix is a structure which consists of rows and columns.

Logic behind matrix multiplication:

• When you want to multiply two matrices, there are some points to be noted.
• First, columns of first matrix and rows of second matrix should be equal.
• Iterate through each row of matrix1 and each column of matrix2 and add the elements.
• Final result matrix rows should be equal to matrix1. The resultant matrix column should be equal to matrix2.

Program implementation:

• It starts with including the built in package java.util.Scanner.
• A public class is created with main() function.
• A scanner object gets assigned with System input.
• The dimensions of two matrices (rows and columns) received from the user. The columns of first matrix are equal to the rows of second matrix.
• The values for first and second matrices are get assigned from user input.
• Using three for loops, the rows are iterated with columns and added its value.
• Finally, it gets assigned to result_matrix.
• At last, the result_matrix is displayed in the screen.

Program:

import java.util.Scanner;

public class MMultiplicationExample {

    public static void main(String[] args) {

        Scanner s1 = new Scanner(System.in);

        // Get the dimensions of matrix

        System.out.print("Enter rows for first matrix: ");

        int r1 = s1.nextInt();

        System.out.print("Enter columns for first matrix / rows for second matrix: ");

        int cR = s1.nextInt();

        System.out.print("Enter columns for second matrix: ");

        int c2 = s1.nextInt();

        // Let us Initialize matrices

        int[][] matrix_1 = new int[r1][cR];

        int[][] matrix_2 = new int[cR][c2];

        int[][] result_matrix = new int[r1][c2];

        // read the input for Matrix 1

        System.out.println("Enter the elements for the first matrix:");

        for (int i = 0; i < r1; i++) {

            for (int j = 0; j < cR; j++) {

                matrix_1[i][j] = s1.nextInt();

            }

        }

        //read the input for Matrix 2

        System.out.println("Enter the elements for the second matrix:");

        for (int i = 0; i < cR; i++) {

            for (int j = 0; j < c2; j++) {

                matrix_2[i][j] = s1.nextInt();

            }

        }

        // Multiply the matrices

        for (int i = 0; i < r1; i++) {

            for (int j = 0; j < c2; j++) {

                result_matrix[i][j] = 0;

                for (int k = 0; k < cR; k++) {

                    result_matrix[i][j] += matrix_1[i][k] * matrix_2[k][j];

                }

            }

        }

        // Display the Resultant matrix

        System.out.println("Here is the Resultant matrix:");

        for (int i = 0; i < r1; i++) {

            for (int j = 0; j < c2; j++) {

                System.out.print(result_matrix[i][j] + " ");

            }

            System.out.println();

        }

        s1.close();

    }

}

Output:

C:\raji\blog>javac MMultiplicationExample.java

C:\raji\blog>java MMultiplicationExample

Enter rows for first matrix: 3

Enter columns for first matrix / rows for second matrix: 2

Enter columns for second matrix: 2

Enter the elements for the first matrix:

1

2

3

4

5

6

Enter the elements for the second matrix:

3

6

9

2

Here is the Resultant matrix:

21 10

45 26

69 42

That’s all. The java implementation of Matrix Multiplication is done. Hope, you are interested in this code. Keep coding.