java.util.Stack 的迭代器中是否有错误?

Here is the code that I was trying.

import java.util.*;
import java.util.Stack;

public class Main {
    public static void main(String[] args) {
        RobStack<Integer> rstack = new RobStack<Integer>(); // Correct Implementation
        Stack<Integer> jstack = new Stack<Integer>(); // Default Java Implementation
        rstack.push(0); jstack.push(0);
        rstack.push(1); jstack.push(1);
        rstack.push(2); jstack.push(2);
        rstack.push(3); jstack.push(3);

        System.out.print("Algo Stack: ");
        for (int i : rstack)
            System.out.print(i + " ");
        System.out.print("
Java Stack: ");
        for (int i : jstack)
            System.out.print(i + " ");
    }

}

上述程序的输出如下:

Algo Stack: 3 2 1 0 
Java Stack: 0 1 2 3 

在上面的代码中，jstack 使用默认的 Java 实现，rstack 使用 Robert Sedgewick 为他的算法类提供的实现.我发现 Robert 教授的实现工作正常，但 java.util.Stack 实现失败.