Java Program to Multiply to Matrix Using Multi-Dimensional Arrays

In this article, we will understand how to multiply to matrix using multi-dimensional arrays. The matrix has a row and column arrangement of its elements. A matrix with m rows and n columns can be called as m × n matrix.

Individual entries in the matrix are called element and can be represented by a[i][j] which suggests that the element a is present in the ith row and jth column.

Below is a demonstration of the same −

Suppose our input is −

First matrix:
2 3 4
5 2 3
4 6 9

Second matrix:
1 5 3
5 6 3
8 1 5

The desired output would be −

The product of two matrices is:
49 32 35
39 40 36
106 65 75

Algorithm

Step 1 - START
Step 2 - Declare three integer matrices namely input_matrix_1, input_matrix_1 and resultant_matrix
Step 3 - Define the values.
Step 4 - Iterate over each element of the both the matrices using for-loop, multiply the element at [i][j] position of the first matrix with each element of the row of the second matrix and add the values, store the value at [i][j] position of the resultant matrix. Repeat this for each element of the first matrix.
Step 5 - Display the result
Step 5 - Stop

Example 1

Here, we bind all the operations together under the ‘main’ function.

public class MultiplyMatrices {
   public static void main(String[] args) {
      int matrix_size = 3;
      int[][] input_matrix_1 = {
         {2, 3, 4},
         {5, 2, 3},
         {4, 6, 9}
      };
      System.out.println("The first matrix is defined as: ");
      for (int i = 0; i < matrix_size; i++) {
         for (int j = 0; j < matrix_size; j++) {
            System.out.print(input_matrix_1[i][j] + " ");
         }
         System.out.println();
      }
      int[][] input_matrix_2 = {
         {1, 5, 3},
         {5, 6, 3},
         {8, 1, 5}
      };
      System.out.println("The second matrix is defined as: ");
      for (int i = 0; i < matrix_size; i++) {
         for (int j = 0; j < matrix_size; j++) {
            System.out.print(input_matrix_2[i][j] + " ");
         }
      System.out.println();
   }
   int[][] resultant_matrix = new int[matrix_size][matrix_size];
   for(int i = 0; i < matrix_size; i++) {
      for (int j = 0; j < matrix_size; j++) {
         for (int k = 0; k < matrix_size; k++) {
            resultant_matrix[i][j] += input_matrix_1[i][k] * input_matrix_2[k][j];
         }
      }
   }
   System.out.println("\n The product of two matrices is: ");
   for(int[] row : resultant_matrix) {
      for (int column : row) {
         System.out.print(column + " ");
      }
      System.out.println();
      }
   }
}

Output

The first matrix is defined as:
2 3 4
5 2 3
4 6 9

The second matrix is defined as:
1 5 3
5 6 3
8 1 5

The product of two matrices is:
49 32 35
39 40 36
106 65 75

Example 2

Here, we encapsulate the operations into functions exhibiting object-oriented programming.

public class MultiplyMatrices {
   static int matrix_size = 3;
   static void multiply(int input_matrix_1[][], int input_matrix_2[][]){
      int[][] resultant_matrix = new int[matrix_size][matrix_size];
      for(int i = 0; i < matrix_size; i++) {
         for (int j = 0; j < matrix_size; j++) {
            for (int k = 0; k < matrix_size; k++) {
               resultant_matrix[i][j] += input_matrix_1[i][k] * input_matrix_2[k][j];
            }
         }
      }
      System.out.println("\n The product of two matrices is: ");
      for(int[] row : resultant_matrix) {
         for (int column : row) {
            System.out.print(column + " ");
         }
         System.out.println();
      }
   }
   public static void main(String[] args) {
      int matrix_size = 3;
      int[][] input_matrix_1 = {
         {2, 3, 4},
         {5, 2, 3},
         {4, 6, 9}
      };
      System.out.println("The first matrix is defined as: ");
      for (int i = 0; i < matrix_size; i++) {
         for (int j = 0; j < matrix_size; j++) {
            System.out.print(input_matrix_1[i][j] + " ");
         }
      System.out.println();
      }
      int[][] input_matrix_2 = { {1, 5, 3},
         {5, 6, 3},
         {8, 1, 5}
      };
      System.out.println("The second matrix is defined as: ");
      for (int i = 0; i < matrix_size; i++) {
         for (int j = 0; j < matrix_size; j++) {
            System.out.print(input_matrix_2[i][j] + " ");
         }
         System.out.println();
      }
      multiply(input_matrix_1, input_matrix_2);
   }
}

Output

The first matrix is defined as:
2 3 4
5 2 3
4 6 9
The second matrix is defined as:
1 5 3
5 6 3
8 1 5

The product of two matrices is:
49 32 35
39 40 36
106 65 75