# 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;
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.