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

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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