Answer:
The program in Java is as follows:
import java.util.*;
public class Main{
 public static void main(String[] args) {
     int n;
     Scanner input = new Scanner(System.in);
  System.out.print("Size of array: ");
  n = input.nextInt();
  int count = 1;
  int[][] arr = new int[n][n];
  for(int i = 0; i<n;i++){
      for(int j = 0; j<n;j++){
          arr[i][j] = count;
          count++;      }  }
  for(int i = 0; i<n;i++){
      for(int j = 0; j<n; j++){
          System.out.printf(arr[i][j]+" ");      }
      System.out.println();  }	}}
Explanation:
This declares the size of the array
     int n;
     Scanner input = new Scanner(System.in);
This prompts the user for size of array
  System.out.print("Size of array: ");
This gets input for size of array
  n = input.nextInt();
This initializes the array element to 1
  int count = 1;
This creates a 2d array
  int[][] arr = new int[n][n];
This iterates through the rows
  for(int i = 0; i<n;i++){
This iterates through the columns
      for(int j = 0; j<n;j++){
This populates the array
          arr[i][j] = count;
          count++;      }  }
The following nested loop prints the array elements
  for(int i = 0; i<n;i++){
      for(int j = 0; j<n; j++){
          System.out.printf(arr[i][j]+" ");      }
      System.out.println();  }	}}