# Multiply matrices java – Java Program to Multiply Two Matrices

Multiply matrices java: In the previous article, we have discussed Java Program to Subtract Two Matrices

In this article we are going to see how we can write a program to calculate the product of two matrices in JAVA language.

## Java Program to Multiply Two Matrices

A 3*3 Matrix is having 3 rows and 3 columns where this 3*3 represents the dimension of the matrix. Means there are 3*3 i.e. total 9 elements in a 3*3 Matrix.

Let’s understand it in more simpler way.

                   | A00   A01   A02 |
Matrix A =  | A10   A11   A12 |
| A20   A21   A22 | 3*3
• Matrix A represents a 3*3 matrix.
• A‘ represents the matrix element
• Aij‘ represents the matrix element at it’s matrix position/index.
• i‘ represents the row index
• j‘ represents the column index
• Means A00=Aij  where i=0 and j=0A01=aij where i=0 and j=1 and like this.
• Here we have started row value from 0 and column value from 0.

Let’s see different ways to multiply two matrices.

### Method-1: Java Program to Multiply Two Matrices By Static Initialization of Array Elements

Approach:

• Initialize and declare two arrays of size 3×3 with elements.
• Use two for loops to iterate the rows and columns .
• Inside the for loops set all the elements of the resultant matrix to 0, and there create another loop to multiply the elements and store them.
• Print the resultant array.

Program:

import java.util.Scanner;
public class Matrix{
public static void main(String args[])
{
//Scanner class to take input
Scanner scan = new Scanner(System.in);

// Initializing the 3X3 matrix i.e. 2D array
int mat1[][] = {{19,25,32},{40,54,62},{70,20,60}};
int mat2[][] =  {{50,15,10},{98,45,78},{23,73,50}};
int res[][] = new int[3][3];
int row, col ;
// Printing the matrices using our user-defined function
System.out.print("\nMatrix 1 : ");
printMatrix(mat1);
System.out.print("\nMatrix 2 : ");
printMatrix(mat2);

// Loops to find product of two matrices
for(row=0;row<3;row++)
for(col=0;col<3;col++)
{
// Initializes the array element to zero first
res[row][col] = 0;
for(int i = 0;i<3;i++)
res[row][col]=mat1[row][i]*mat2[i][col];
}
System.out.print("\nAfter multiplication of both the matices : ");
printMatrix(res);
}

// Function to print the matrix
static void printMatrix(int arr[][])
{
int row, col;
// Loop to print the elements
for(row=0;row<3;row++)
{
// Used for formatting
System.out.print("\n");
for(col=0;col<3;col++)
{
System.out.print(arr[row][col]+" ");
}
}
System.out.print("\n");
}
}


Output:

Matrix 1 :
19 25 32
40 54 62
70 20 60

Matrix 2 :
50 15 10
98 45 78
23 73 50

After multiplication of both the matices :
736   2336 1600
1426 4526 3100
1380 4380 3000

### Method-2: Java Program to Multiply Two Matrices By Dynamic Initialization of Array Elements

Approach:

• Initialize and declare two arrays of size 3×3.
• Ask the user for input and store them in the arrays using two for loops.
• Use two for loops to iterate the rows and columns.
• Inside the for loops set all the elements of the resultant matrix to 0, and there create another loop to multiply the elements and store them.
• Print the resultant array.

Program:

import java.util.Scanner;
public class Matrix{
public static void main(String args[])
{
//Scanner class to take input
Scanner scan = new Scanner(System.in);

// Initializing the 3X3 matrix i.e. 2D array
int mat1[][] = new int[3][3];
int mat2[][] =  new int[3][3];
int res[][] = new int[3][3];
int row, col ;

// Taking matrix1 input
System.out.print("\nEnter the first matrix elements : ");
for(row=0;row<3;row++)
for(col=0;col<3;col++)
mat1[row][col] = scan.nextInt();

System.out.print("\nMatrix 1 :");
//calling the printMatrix() method to print matrix 1
printMatrix(mat1);

// Taking matrix2 input
System.out.print("\nEnter the second matrix elements : ");
for(row=0;row<3;row++)
for(col=0;col<3;col++)
mat2[row][col] = scan.nextInt();

System.out.print("\nMatrix 2 :");
//calling the printMatrix() method to print matrix 1
printMatrix(mat2);

// Loops to find product of two matrices
for(row=0;row<3;row++)
for(col=0;col<3;col++)
{
// Initializes the array element to zero first
res[row][col] = 0;
for(int i = 0;i<3;i++)
res[row][col]+=mat1[row][i]*mat2[i][col];
}
System.out.print("\nAfter multiplication of both the matrices : ");
printMatrix(res);
}

// Function to print the matrix
static void printMatrix(int arr[][])
{
int row, col;
// Loop to print the elements
for(row=0;row<3;row++)
{
// Used for formatting
System.out.print("\n");
for(col=0;col<3;col++)
{
System.out.print(arr[row][col]+" ");
}
}
System.out.print("\n");
}
}


Output:

Enter the first matrix elements : 1 2 3 4 5 6 7 8 9
Matrix 1 :
1 2 3
4 5 6
7 8 9

Enter the second matrix elements : 1 2 3 4 5 6 7 8 9
Matrix 2 :
1 2 3
4 5 6
7 8 9

After multiplication of both the matrices :
30 36 42
66 81 96
102 126 150

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