# Sum of principal diagonal of a Matrix in Java

Hello coders, today we will see **how to find the sum of principal diagonal in a matrix in Java**.

A matrix is nothing but a 2D array, and since we need to work with diagonal therefore we need a square matrix, that is, the same number of rows and columns.

Have a look at the below matrix:

A1 A2 A3

B1 B2 B3

C1 C2 C3

Here the principal diagonal is A1 – B2- C3, and our task is to find the sum of these elements.

It has to be noted that the matrix can be of any dimension, though it needs to be a square matrix.

## Java program to find Sum of the principal diagonal of a Matrix

import java.util.*; public class test { public static void main(String[] args) { Scanner sc=new Scanner(System.in); int arr[][]=new int[3][3]; int dsum=0; System.out.println("Enter elements in matrix"); for(int i=0;i<=2;i++) { for(int j=0;j<=2;j++) { arr[i][j]=sc.nextInt(); if(i==j) { dsum=dsum+arr[i][j]; } } } System.out.println("The sum of principal diagonal is "+dsum); } }

The above code will generate the following result:

Enter elements in matrix 13 14 15 32 97 16 23 21 45 The sum of principal diagonal is 155

Hope this helped you out.

Have a nice day ahead.

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