# Java Program to find Multiplication of Diagonal Elements of a Matrix

In the previous article, we have discussed Java Program to find Sum of Diagonal Elements of a Matrix

In this article we are going to see how we can write a program to calculate the product of both diagonal elements of a matrix in JAVA language.

## Program to find Multiplication of Diagonal Elements of a Matrix

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 find Multiplication of Diagonal Elements of a Matrix.

### Method-1: Java Program to find Multiplication of Diagonal Elements of a Matrix By Static Initialization of Array Elements

Approach:

• Initialize an array of size 3×3 with values.
• Show the array to the user.
• Use two for loops to iterate the rows and columns, then multiply both the diagonal elements.
• Print the output.

Program:

public class Matrix{
public static void main(String args[])
{
// Initializing the 3X3 matrix i.e. 2D array
int arr[][] = {{1,2,3},{4,5,6},{7,8,9}};
int row, col;
long primaryProd = 1, secondaryProd =1;
// Printing the matrix using our user-defined function
printMatrix(arr);

// Loops to find the product
for(row=0;row<3;row++)
for(col=0;col<3;col++)
{
// Only goes in if the element is a diagonal element
if(row==col)
primaryProd *= arr[row][col];
if(row+col==2)
secondaryProd *= arr[row][col];
}
System.out.println("\nProduct of left diagonal : "+primaryProd);
System.out.println("Product of right diagonal : "+secondaryProd);

System.out.println("The product of both diagonal elements are : "+(primaryProd*secondaryProd));
}

// Function to print the matrix
static void printMatrix(int arr[][])
{
int row, col;
System.out.print("The matrix elements are");
// 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]+" ");
}
}
}
}


Output:

The matrix elements are
1 2 3
4 5 6
7 8 9
Product of left diagonal : 45
Product of right diagonal : 105
The product of both diagonal elements are : 4725

### Method-2: Java Program to find Multiplication of Diagonal Elements of a Matrix By Dynamic Initialization of Array Elements

Approach:

• Initialize an array of size 3×3.
• Ask the user for input.
• Use two for loops to iterate the rows and columns to input the array elements.
• Use two for loops to iterate the rows and columns, then multiply both the diagonal elements.
• Print the output.

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);

// Delclaring the 3X3 matrix i.e. 2D array
int arr[][] = new int;
int row, col, primaryProd = 1, secondaryProd=1;

// Taking the matrix as input
System.out.println("Enter the matrix elements : ");
for(row=0;row<3;row++)
for(col=0;col<3;col++)
arr[row][col] = scan.nextInt();

System.out.print("Matrix : ");
// 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]+" ");
}
}

// Loops to find the product
for(row=0;row<3;row++)
for(col=0;col<3;col++)
{
// Only goes in if the element is a diagonal element
if(row==col)
primaryProd *= arr[row][col];
if(row+col==2)
secondaryProd *= arr[row][col];
}
System.out.println("\nThe product of left diagonal elements is : "+primaryProd);
System.out.println("The product of right diagonal elements is : "+secondaryProd);
System.out.println("The product of both diagonal elements is : "+(primaryProd*secondaryProd));
}
}


Output:

Enter the matrix elements : 1 2 3 4 5 6 7 8 9
Matrix :
1 2 3
4 5 6
7 8 9
The product of left diagonal elements is : 45
The product of right diagonal elements is : 105
The product of both diagonal elements is : 4725

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