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Java Program to Multiply Two Matrices [Matrix Multiplication]

Question:

Write a Program in Java to input two 2-D arrays and perform Matrix Multiplication:

Illustration:

matrix multiplication java program

Solution:

/**
* The class MatrixMultiplication inputs 2 Matrices and performs Matrix Multiplication on them
* @author : www.guideforschool.com
* @Program Type : BlueJ Program - Java
*/

import java.util.*;
class MatrixMultiplication
{
    void printMatrix(int P[][], int r, int c) // Funtion for printing an array
    {
        for(int i=0; i<r; i++)
        {
            for(int j=0; j<c; j++)
            {
                System.out.print(P[i][j]+"\t");
            }
            System.out.println();
        }
    }
    
    public static void main(String args[])throws Exception
    {
        MatrixMultiplication ob = new MatrixMultiplication();
        Scanner sc = new Scanner(System.in);
        
        System.out.print("Enter no. of rows of 1st Matrix : ");
        int r1=sc.nextInt();
        System.out.print("Enter no. of columns of 1st Matrix : ");
        int c1=sc.nextInt();
        
        System.out.print("Enter no. of rows of 2nd Matrix : ");
        int r2=sc.nextInt();
        System.out.print("Enter no. of columns of 2nd Matrix : ");
        int c2=sc.nextInt();
        
        if(c1 != r2) // Condition for Multiplication to be possible
        {
            System.out.println("Matrix Multiplication of the given order is not possible");
        }
        else
        {
            int A[][]=new int[r1][c1]; // Array to store 1st Matrix
            int B[][]=new int[r2][c2]; // Array to store 2nd Matrix
            int C[][]=new int[r1][c2]; // Array to store Result of Multiplication of 2 Matrices
            
            System.out.println("*************************");
            System.out.println("Inputting the 1st Matrix");
            System.out.println("*************************");
            for(int i=0; i<r1; i++)
            {
                for(int j=0; j<c1; j++)
                {
                    System.out.print("Enter an element : ");
                    A[i][j]=sc.nextInt();
                }
            }
            System.out.println("*************************");
            System.out.println("Inputting the 2nd Matrix");
            System.out.println("*************************");
            for(int i=0; i<r2; i++)
            {
                for(int j=0; j<c2; j++)
                {
                    System.out.print("Enter an element : ");
                    B[i][j]=sc.nextInt();
                }
            }
            
            /* Matrix Multiplication Starts Here */
            
            int sum = 0;
            for(int i=0; i<r1; i++)
            {
                for(int j=0; j<c2; j++)
                {
                    for(int k=0; k<c1; k++)
                    {
                        sum = sum + A[i][k]*B[k][j];
                    }
                    C[i][j]=sum;
                    sum=0;
                }
            }
            
            /* Printing all the Matrices */
            System.out.println("n*************************");
            System.out.println("          Output         ");
            System.out.println("*************************");
            System.out.println("The 1st Matrix is");
            ob.printMatrix(A,r1,c1);
            System.out.println("*************************");
            System.out.println("The 2nd Matrix is");
            ob.printMatrix(B,r2,c2);
            System.out.println("************************************");
            System.out.println("The Result of Multiplication is");
            ob.printMatrix(C,r1,c2);
        }
    }
}

Output:

Enter no. of rows of 1st Matrix : 2
Enter no. of columns of 1st Matrix : 3
Enter no. of rows of 2nd Matrix : 3
Enter no. of columns of 2nd Matrix : 2
*************************
Inputting the 1st Matrix
*************************
Enter an element : 8
Enter an element : 1
Enter an element : 2
Enter an element : -5
Enter an element : 6
Enter an element : 7
*************************
Inputting the 2nd Matrix
*************************
Enter an element : -5
Enter an element : 1
Enter an element : 0
Enter an element : 2
Enter an element : -11
Enter an element : 7

*************************
Output
*************************
The 1st Matrix is
8 1 2
-5 6 7
*************************
The 2nd Matrix is
-5 1
0 2
-11 7
************************************
The Result of Multiplication is
-62 24
-52 56

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