Stack迭代器算不算是bug？

import java.util.*;

class test {
	public static void main(String[] strs) {
		Stack s = new Stack();
		s.add("one");
		s.add("two");
		s.add("three");
		s.add("four");
		System.err.println(s);
		Iterator i = s.iterator();
		while(i.hasNext()) {
			System.err.println(i.next());
		}
	}
}

输出：

[one, two, three, four]
one
two
three
four