# Check diagonals 2d array java – Java Program to Check Whether the Matrix is a Diagonal Matrix or Not

Check diagonals 2d array java: In the previous article, we have discussed Java Program to Check Whether the Matrix is a Markov Matrix or Not

In this article we are going to see how we can check if a matrix is a diagonal matrix or not in JAVA language.

## Java Program to Check Whether the Matrix is a Diagonal Matrix or Not

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=0,  A01=aij where i=0 and j=1 and like this.
• Here we have started row value from 0 and column value from 0.

Diagonal matrix is a matrix which has all zero elements at its non-main diagonal places.

For example:

2 0 0
0 5 0
0 0 7

Let’s see different ways to check Diagonal Matrix.

### Method-1: Java Program to Check Whether the Matrix is a Diagonal Matrix or Not By Static Initialization of Array Elements

Approach:

• Initialize and declare one array of size 3×3 with elements.
• Check if there are any elements at nondiagonal place except zero.
• If there are no non-zero elements it is a diagonal matrix.

Program:

public class matrix{
public static void main(String args[])
{
// Initializing the 3X3 matrix i.e. 2D array
int arr[][] = {{19,0,0},{0,54,0},{0,0,60}};
int row, col;

System.out.print("The matrix elements are:");
printMatrix(arr);

if(checkDiagonal(arr))
System.out.println("\nIt is a diagonal matrix");
else
System.out.println("\nIt is not a diagonal matrix");

}

// 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]+" ");
}
}
}

// Checks whether the matrix is a diagonal matrix or not
static boolean checkDiagonal(int arr[][])
{
int row, col;
for(row =0;row<3;row++)
for(col=0;col<3;col++)
if(row!=col&&arr[row][col]!=0)
return false;
return true;
}

}


Output:

The matrix elements are:
19 0 0
0 54 0
0 0 60

It is a diagonal matrix

### Method-2: Java Program to Check Whether the Matrix is a Diagonal Matrix or Not By Dynamic Initialization of Array Elements

Approach:

• Declare one array of size 3×3.
• Use two for loops to take input of array elements.
• Check if there are any elements at nondiagonal place except zero.
• If there are no non-zero elements it is a diagonal matrix.

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 arr[][] = new int[3][3];
int row, col;

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

System.out.print("The matrix elements are:");
printMatrix(arr);

if(checkDiagonal(arr))
System.out.println("\nIt is a diagonal matrix");
else
System.out.println("\nIt is not a diagonal matrix");

}

// Method 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]+" ");
}
}
}

// Checks whether the matrix is a diagonal matrix or not
static boolean checkDiagonal(int arr[][])
{
int row, col;
for(row =0;row<3;row++)
for(col=0;col<3;col++)
if(row!=col&&arr[row][col]!=0)
return false;
return true;
}

}


Output:

Enter matrix elements : 1 0 0 0 3 0 0 0 2
The matrix elements are:
1 0 0
0 3 0
0 0 2
It is a diagonal matrix

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