Question

import java.util.Scanner;

public class Test {
 public static void main(String[] args) {
  Scanner sc = new Scanner(System.in);
  int n = sc.nextInt();
  int[] v = new int[n];
 }
}

Is there any problem in doing this?

Answer 1

No. (Other than n might be negative, or be huge causing a Denial-of-Service (DoS) condition.)

With arrays you can’t change the size later. You have to create a new array, copy the contents and switch all references over.