Convert from Decimal to Binary using Stacks in Java

Problem:

To convert a number from decimal to binary, you simply divide by two until a quotient of zero is reached, then use the successive remainders in reverse order as the binary representation. Use a stack to store the remainder of the division and finally print the binary representation. The first line of input n is the number test cases. Each test case begins with an integer t representing the number of integers in the list, then t integers follow.

Output:

3
5
7
10

101
111
1010

Solution:

import java.util.Scanner;
import java.util.Stack;

public class ProblemD {

 public static void main(String[] args) {
  
  Stack<Integer> stack = new Stack<Integer>();
  
  Scanner scan = new Scanner(System.in);
  
  int numberOfExpressions = scan.nextInt();
  int[] num = new int[numberOfExpressions];
  
  for (int i = 0;i<numberOfExpressions;i++)
  {
   num[i] = scan.nextInt();
  }
  
  for (int i = 0;i<numberOfExpressions;i++)
  {
   if (num[i] == 0) {
                System.out.println("0000");
   } else if (num[i] == 1) {
                System.out.println("0001");
   } else {
                while (num[i] != 0) {
                        int a = num[i] / 2;
                        int b = num[i] % 2;
                        stack.push(b);
                        num[i] = a;
                }
        }
   
   while (!stack.empty()) {
                System.out.print(stack.pop());
        }

   System.out.println(" ");
  }

 }
}