为什么这不能从我的java列表中删除重复项呢？

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class RemoveDuplicatesFromList {
    public static void main(String[] args) {
        List<Integer> numbers = new ArrayList<>();
        numbers.add(1);
        numbers.add(2);
        numbers.add(3);
        numbers.add(2);
        numbers.add(4);
        numbers.add(1);

        List<Integer> uniqueNumbers = new ArrayList<>();
        Set<Integer> set = new HashSet<>();

        for (Integer number : numbers) {
            if (!set.contains(number)) {
                set.add(number);
                uniqueNumbers.add(number);
            }
        }

        System.out.println("Original List: " + numbers);
        System.out.println("List without duplicates: " + uniqueNumbers);
    }
}