Write a program to declare a square matrix a[][] of order [M × M]. Allow the user to input positive integers into this matrix. Perform the following tasks on the matrix:

- Sort the boundary elements in descending order using any standard sorting technique and rearrange them in the matrix.
- Calculate he sum of the boundary elements.
- Display the original matrix, rearranged matrix and the sum of the boundary elements.

```
import java.io.*;
class Boundary{
public static void main(String args[])throws IOException{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
System.out.print("M = ");
int m = Integer.parseInt(br.readLine());
int a[][] = new int[m][m];
int b[] = new int[2 * m + 2 * (m - 2)];
int index = 0;
int sum = 0;
System.out.println("Enter positive integers:");
for(int i = 0; i < m; i++){
for(int j = 0; j < m; j++){
a[i][j] = Math.abs(Integer.parseInt(br.readLine()));
if(i == 0 || j == 0 || i == m - 1 || j == m - 1){
b[index++] = a[i][j];
sum += a[i][j];
}
}
}
System.out.println("Original matrix:");
for(int i = 0; i < m; i++){
for(int j = 0; j < m; j++){
System.out.print(a[i][j] + "\t");
}
System.out.println();
}
for(int i = 0; i < b.length; i++){
for(int j = 0; j < b.length - 1 - i; j++){
if(b[j] < b[j + 1]){
int temp = b[j];
b[j] = b[j + 1];
b[j + 1] = temp;
}
}
}
index = 0;
for(int i = 0; i < m; i++)
a[0][i] = b[index++];
for(int i = 1; i < m; i++)
a[i][m - 1] = b[index++];
for(int i = m - 2; i >= 0; i--)
a[m - 1][i] = b[index++];
for(int i = m - 2; i >= 1; i--)
a[i][0] = b[index++];
System.out.println("Rearranged matrix:");
for(int i = 0; i < m; i++){
for(int j = 0; j < m; j++){
System.out.print(a[i][j] + "\t");
}
System.out.println();
}
System.out.println("Sum of boundary elements: " + sum);
}
}
```