Remove duplicates from sorted array (in-place)

import java.util.List;

class Main {
    public static void main(String[] args) {
        /**
         * Problem: Remove duplicates from sorted array (in-place)
         * 
         * Input: nums = [1, 1, 2, 2, 3, 4, 4]
         * Output: 4 (and nums becomes [1, 2, 3, 4, _, _, _])
         */
         
         int[] nums = {1, 1, 2, 2, 3, 4, 4};
         
         // I need to remove duplicated elements and fill out the remaining slots
         
         // I think we can use Two pointers in the same direction
         // We need two pointers. One moving slow and pointing to the slow where 
         // we can put a non duplicated element
         
         int slow = 0;
         for (int fast = 0; fast < nums.length; fast++) { // Time O(n)
             
             if (nums[slow] != nums[fast]) {
                 slow++;
                 nums[slow] = nums[fast];
             }
         }
         
         // Time complexity O(n)
         // Space complexity O(1)
         
         int amountUniqueElements = slow + 1;
         
         System.out.println("Unique elements: " + amountUniqueElements);
         System.out.println("nums after removing duplicates:" + nums);
         
         // Also, we can use Java Stream to create a stream of Integers and then 
         // collecting them to a Set to remove duplicates. However, we will lose 
         // how many remaining slots we need to fill out with '_' character. 
         // Nonetheless, thinking carefully, I think having a Set we can not add
         // more than one '_' character. That would require using another data 
         // structure such as List
    }
}