Program for Matrix Multiplication in Java

August 20, 2021

Matrix Multiplication in Java

We can multiply two matrices in java using binary * operator. In case of matrix multiplication, one row element of first matrix is multiplied by all columns of second matrix. In this article, we will discuss about the multiplication of matrix in java

Matrix Multiplication in Java

Obtaining a single matrix from the entries of two matrices by using a binary operation is known as Matrix multiplication. In simpler terms, if two matrices matrix1 and matrix2 of order a*b and b*c are multiplied, the matrix obtained is of the order a*c.

First Matrix :
1 1 1 
2 2 2 
3 3 3 
4 4 4 

Second Matrix :
1 1 1 1 
2 2 2 2 
3 3 3 3 

Resultant Matrix:
6 6 6 6 
12 12 12 12 
18 18 18 18 
24 24 24 24

Approach

Take the two matrices as input to be multiplies.
Create the new matrix mat3 to store the product of two matrices.
Traverse each element of the two metrices and multiply them.
Store this product in the new matrix at the corresponding index.
Print the Resultant matrix.

Code in Java

import java.util.*;
public class Main
{
    public static void matrixMultiply(int r1,int c1,int mat1[][],int r2,int c2,int mat2[][])
    {
        
        int i, j, k;
        int mat3[][] = new int[r1][c2];
  

        for (i = 0; i < r1; i++) 
        {
            for (j = 0; j < c2; j++) 
            {
                for (k = 0; k < r2; k++)
                    mat3[i][j] += mat1[i][k] * mat2[k][j];
            }
        }
  
     
        System.out.println("\nResultant Matrix:");
        for(i=0;i<r1;i++)
        {
            for(j=0;j<c1;j++)
                System.out.print(mat3[i][j]+" ");
            System.out.println();
        }
  
    }
	public static void main(String[] args) {
	    Scanner sc=new Scanner(System.in);
	    System.out.println("Enter the number of rows of first matrix ");
	    int row1=sc.nextInt();
	    System.out.println("Enter the number of columns of first matrix ");
	    int col1=sc.nextInt();
	    System.out.println("Enter the elements of first matrix");
	    
	    int matrix1[][]=new int[row1][col1];
	    for(int i=0;i<row1;i++)
	    {
	        for(int j=0;j<col1;j++)
	        {
	            matrix1[i][j]=sc.nextInt();
	        }
	    }
	    System.out.println("Enter the number of rows of second matrix ");
	    int row2=sc.nextInt();
	    System.out.println("Enter the number of columns of second matrix ");
	    int col2=sc.nextInt();
	    System.out.println("Enter the elements of second matrix");
	    
	    int matrix2[][]=new int[row2][col2];
	    for(int i=0;i<row2;i++)
	    {
	        for(int j=0;j<col2;j++)
	        {
	            matrix2[i][j]=sc.nextInt();
	        }
	    }
	    
	    matrixMultiply(row1,col1,matrix1,row2,col2,matrix2);
	}
}

Output :

Enter the number of rows of first matrix
4
Enter the number of columns of first matrix
3
Enter the elements of first matrix
1 1 1
2 2 2
3 3 3 
4 4 4

Enter the number of rows of second matrix
3
Enter the number of columns of second matrix
4
Enter the elements of second matrix
1 1 1 1 
2 2 2 2 
3 3 3 3

Resultant Matrix:
6 6 6 
12 12 12
18 18 18 
24 24 24