Java Program to determine whether a given matrix is an identity matrix

In this program, we need to check whether the given matrix is an identity matrix.

Identity Matrix

A matrix is said to be an identity matrix if it is a square matrix in which elements of principle diagonal are ones, and the rest of the elements are zeroes.

Algorithm

STEP 1: START
STEP 2: DEFINE rows, cols
STEP 3: SET flag =true
STEP 4: INITIALIZE matrix a[][] ={{1,0,0},{0,1,0}, {0,0,1}}
STEP 5: rows = a.length
STEP 6: cols = a[0].length
STEP 7: if(rows!=cols)
then
PRINT "Matrix should be a square matrix"
else
go to step 8
STEP 8: REPEAT STEP 9 to STEP 11 UNTIL i<rows
//for(i=0; i<rows; i++)
STEP 9: REPEAT STEP 10 to STEP 11 UNTIL j<cols
//for(j=0; j<cols; j++)
STEP 10: if(i==j && a[i][j]== 1) then
SET flag =false
break
STEP 11: if( i!=j && a[i][j]!=0)
SET flag = false
break
STEP 12: if(flag)
then PRINT ("Given matrix is an identity matrix")
else
PRINT ("Given matrix is not an identity matrix")
STEP 13: END

Program:

public class IdentityMatrix   
{  
    public static void main(String[] args) {  
        int rows, cols;  
        boolean flag = true;  
          
        //Initialize matrix a  
        int a[][] = {     
                        {1, 0, 0},  
                        {0, 1, 0},  
                        {0, 0, 1}  
                    };  
          
        //Calculates the number of rows and columns present in the given matrix  
  
          rows = a.length;  
        cols = a[0].length;  
          
        //Checks whether given matrix is a square matrix or not  
        if(rows != cols){  
            System.out.println("Matrix should be a square matrix");  
        }  
        else {  
            //Checks if diagonal elements are equal to 1 and rest of elements are 0  
            for(int i = 0; i < rows; i++){  
                for(int j = 0; j < cols; j++){  
                  if(i == j && a[i][j] != 1){  
                      flag = false;  
                      break;  
                  }  
                  if(i != j && a[i][j] != 0){  
                      flag = false;  
                      break;  
                  }  
                }  
            }  
              
            if(flag)  
                System.out.println("Given matrix is an identity matrix");  
            else  
                System.out.println("Given matrix is not an identity matrix");  
        }  
    }  
}  

Output: