Stack subclasses Vector which already supports this, try this...

stack.toArray(array)

Here is the Javadoc for this.

You can use Stream APIs of Java 8

int[] intArray = Arrays.stream(array).mapToInt(Integer::intValue).toArray();

You can convert entire string and then you get the toCharArray method separately characters in an array

Scanner t = new Scanner(System.in);
     int x = t.nextInt();
     char[] xd = String.valueOf(x).toCharArray();

    for (int i = 0; i < xd.length; i++) {
        System.out.println(xd[i]);
    }

Another way of doing this would be:

int test = 12345;
        int[] testArray = new int[String.valueOf(test).length()];

And then looping over it.

It has to be a raw Stack[] or you can use List<Stack<YourClass>> lstStack = new ArrayList<Stack<YourClass>>().

In this case, I would prefer to use

List<Stack<Integer>> lstStack = new ArrayList<Stack<Integer>>(stackLength);

Try something more like this...

Before you are only reading in one number one time, which seems like you want to be used for the size of your array. After this, you continually push the same number onto the stack because you never prompt the user to enter in any other number.

The code below goes one step further than your code in that once you have learned the number from the User and set your array size, you ask for a new number over and over again to populate your array until your array is filled. This can be accomplished by prompting the user to enter a value over and over again in the for loop.

I am not really sure why exactly you need an array to do what you want to do though, consider removing the array and just using the first number entered as your bounds for the for loop rather than the array size. The array data structure is really just a waste of space as the only time you ever use it is to use its length as a stopping point in the for loop

public class NumberReverse {
      public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);


      System.out.print("Enter stack size: ");

      int number = sc.nextInt();
      int[] array = new int[number];

      Stack<Integer> stack = new Stack<Integer>();
      for(int i = 0; i < array.length; i++){
          System.out.println("Enter your number: ");
          int value = sc.nextInt();              
          stack.push(value);
      }

      while (!(stack.isEmpty())) {
          System.out.println(stack.pop());


      }    
    }
}

Based on the comment below consider trying something like the code below. You are only printing out one number for the same reasons that I have listed above...

import java.util.*; 
public class NumberReverse { 
    public static void main(String[] args) { 
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter how many numbers you want to place on the Stack: ");
        int stackSize = sc.nextInt();
        Stack<Integer> stack = new Stack<Integer>();
        for(int i = 0; i < stackSize; i++){ 
            System.out.println("Enter numbers: "); 
            int number = sc.nextInt();  
            stack.push(number); 
        }
        while (!(stack.isEmpty())) { 
            System.out.println(stack.pop()); 
        } 
    } 
}