Java – how to receive user data from the console

My console Java application generates a 3 containing some random numbers × 3 matrix What I want to do is delete some random numbers from the set and allow the user to enter them

So far, I've tried the following, but it doesn't work

package magicsquare;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Random;

public class MagicSquare {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(system.in));
        System.out.print("\n\nEnter the size of the matrix : ");
        int n = Integer.parseInt(br.readLine());
        if (n > 5 && n < 2) {
            System.out.println("Enter a number between 2 to 5 ");
        } else {
            int A[][] = new int[n][n]; // Creating the Magic Matrix
            int i,j,k,t;
            /*Initializing every cell of the matrix with 0 */
            for (i = 0; i < n; i++) {
                for (j = 0; j < n; j++) {
                    A[i][j] = 0;
                }
            }
            /* When the size of the matrix is Odd */
            if (n % 2 != 0) {
                i = 0;
                j = n / 2;
                k = 1;
                while (k <= n * n) {
                    A[i][j] = k++;
                    i--; // Making one step upward
                    j++; // Moving one step to the right 
                    if (i < 0 && j > n - 1) // Condition for the top-right corner element 
                    {
                        i = i + 2;
                        j--;
                    }
                    if (i < 0) // Wrapping around the row if it goes out of boundary 
                    {
                        i = n - 1;
                    }
                    if (j > n - 1) // Wrapping around the column if it goes out of boundary 
                    {
                        j = 0;
                    }
                    if (A[i][j] > 0) // Condition when the cell is already filled
                    {
                        i = i + 2;
                        j--;
                    }
                }
            } /* When the size of the matrix is even */ else {
                k = 1;
                /* Filling the matrix with natural numbers from 1 till n*n */
                for (i = 0; i < n; i++) {
                    for (j = 0; j < n; j++) {
                        A[i][j] = k++;
                    }
                }
                j = n - 1;
                for (i = 0; i < n / 2; i++) {
                    /* swapping corner elements of primary diagonal */
                    t = A[i][i];
                    A[i][i] = A[j][j];
                    A[j][j] = t;
                    /* swapping corner elements of secondary diagonal */
                    t = A[i][j];
                    A[i][j] = A[j][i];
                    A[j][i] = t;
                    j--;
                }
            }
            /* Printing the Magic matrix */
            System.out.println("The Magic Matrix of size " + n + "x" + n + " is:");
            for (i = 0; i < n; i++) {
                for (j = 0; j < n; j++) {
                    //remove random element from array
                   Random rand = new Random();   
                  for (i = 0; i < 4 ; i++)
                  {
                  int randomNum1 = rand.nextInt((n-1) - 0 + 1) + 0;
                  int randomNum2 = rand.nextInt((n-1) - 0 + 1) + 0;
                  BufferedReader dr = new BufferedReader(new InputStreamReader(system.in));
                  A[randomNum1][randomNum2] = Integer.parseInt(dr.readLine());
                  }
                    System.out.print(A[i][j] + "\t");
                }
                System.out.println();

            }

        }
    }

}

edit

What I want to happen is that some numbers are missing when the matrix is displayed The user then places the cursor at the missing position and enters a number

Solution

In your code, you allow the user to select multiple numbers for each matrix number displayed, so multiple inputs are required before printing a number Do you want something like this?

/* Printing the Magic matrix */
        System.out.println("The Magic Matrix of size " + n + "x" + n + " is:");
        Random rand = new Random();
        for (i = 0; i < 2; i++) { //lets a user choose 2 numbers to be replaced
            System.out.println("Please input a number: ");
            int randomNum1 = rand.nextInt((n - 1) - 0 + 1) + 0;
            int randomNum2 = rand.nextInt((n - 1) - 0 + 1) + 0;
            BufferedReader dr = new BufferedReader(new InputStreamReader(system.in));
            A[randomNum1][randomNum2] = Integer.parseInt(dr.readLine());
        }

        for (i = 0; i < n; i++) {
            System.out.println("\n");
            for (j = 0; j < n; j++)
                System.out.print(A[i][j] + "\t");
        }
        System.out.println();

    }
}

}

Edit: the same number may be replaced twice by this code