Question:

(a) Sort the boundary elements in descending order using any standard sorting technique and rearrange them in the matrix.

(b) Calculate the sum of the boundary elements.

(c) Display the original matrix, rearranged matrix and sum of the boundary elements.

Code:

import java.util.*;
class SortBoundary
{
    int A[][], B[], m, n; 
    static int sum=0;
 
    void input() //Function for taking all the necessary inputs
    {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the size of the square matrix : ");
        m=sc.nextInt();
        if(m<4 || m>10)
        {
            System.out.println("Invalid Range");
            System.exit(0);
        }
        else
        {
            A = new int[m][m];
            n = m*m;
            B = new int[n]; // 1-D Array to store Boundary Elements
 
            System.out.println("Enter the elements of the Matrix : ");
            for(int i=0;i<m;i++)
            {
                for(int j=0;j<m;j++)
                {
                    System.out.print("Enter a value : ");
                    A[i][j]=sc.nextInt();
                }
            }
        }
    }
 
    /* The below function is used to store Boundary elements 
     * from array A[][] to array B[] 
     */
    void convert()
    {
        int x=0;
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<m;j++)
            {
                if(i == 0 || j == 0 || i == m-1 || j == m-1) // Condition for boundary elements
                {
                    B[x] = A[i][j];
                    x++;
                    sum = sum + A[i][j]; // Finding sum of boundary elements
                }
            }
        }
    }
 
    void sortArray() //Function for sorting Boundary elements stored in array B[]
    {
        int c = 0;
        for(int i=0; i<n-1; i++)
        {
            for(int j=i+1; j<n; j++)
            {
                if(B[i]<B[j]) // for ascending use B[i]>B[j]
                {
                    c = B[i];
                    B[i] = B[j];
                    B[j] = c;
                }
            }
        }
    }
     
    /* Function fillSpiral is filling the boundary of 2-D array in spiral
     * way from the elements of 1-D array
     */
    void fillSpiral()
    {
        int R1=0, R2=m-1, C1=0, C2=m-1, x=0;
 
        for(int i=C1;i<=C2;i++) // accessing the top row
        {
            A[R1][i]=B[x++];
        }
        for(int i =R1+1;i<=R2;i++) // accessing the right column
        {
            A[i][C2]=B[x++];
        }
        for(int i =C2-1;i>=C1;i--) // accessing the bottom row
        {
            A[R2][i]=B[x++];
        }
        for(int i =R2-1;i>=R1+1;i--) // accessing the left column
        {
            A[i][C1]=B[x++];
        }
    }
 
    void printArray() //Function for printing the array A[][]
    {
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<m;j++)
            {
                System.out.print(A[i][j]+"\t");
            }
            System.out.println();
        }
    }
 
    public static void main(String args[])
    {
        SortBoundary ob = new SortBoundary();
        ob.input();
        System.out.println("*********************");
        System.out.println("The original matrix:");
        System.out.println("*********************");
        ob.printArray(); //Printing the original array
        ob.convert(); //Storing Boundary elements to a 1-D array
        ob.sortArray(); //Sorting the 1-D array (i.e. Boundary Elements)
        ob.fillSpiral(); //Storing the sorted Boundary elements back to original 2-D array
 
        System.out.println("*********************");
        System.out.println("The Rearranged matrix:");
        System.out.println("*********************");
        ob.printArray(); //Printing the rearranged array
        System.out.println("*********************");
        System.out.println("The sum of boundary elements is = "+sum); //Printing the sum of boundary elements
    }
}

What I want to accomplish:

I want to fill the original array A with the sorted boundary elements B in a single loop at their respective positions in descending order.In my code I have used 4 different loops for accomplishing this task.Any suggestions or help to make my code better?