堆栈的失败快速迭代器

Question

我想实现一个Fail-Fast Iterator来从我自己的List中删除Entrys并测试它的正确行为。 List包含MyEntry类型的元素。

这些Entrys持有通用值和对下一个条目的引用。

class MyEntry<E>  {

    MyEntry<E> next;
    E o;

    MyEntry() {
        this(null, null);
    }

    MyEntry(E o) {
        this(o, null);
    }

    MyEntry(E o, MyEntry<E> e) {
        this.o = o;
        this.next = e;
    }
}

List本身使用pos Entry跟踪其位置，其行为类似于Stack。现在我想实现一个快速失败的迭代器，它允许我迭代List并删除Entrys而不是抛出UnsupportedOperation异常。

import java.util.Iterator;
import java.util.NoSuchElementException;

public class MyList<E> implements Cloneable, java.lang.Iterable {

    private MyEntry<E> begin;

    private MyEntry<E> pos;


    public MyList() {
        pos = begin = new MyEntry<E>();
    }


    public boolean empty() {
        return begin.next == null;
    }


    public boolean endpos() { 
        return pos.next == null;
    }


    public void reset() {
        pos = begin;
    }

    /**
     * Advances one step in this List.
     *
     * @throws NoSuchElementException if the last Entry of this List already has been reached.
     */
    public void advance() {
        if (endpos()) {
            throw new NoSuchElementException("Already at the end of this List");
        }
        pos = pos.next;
    }

    /**
     * Returns the actual element of this List.
     *
     * @return the actual element
     * @throws RuntimeException if the last Entry of this List already has been reached.
     */
    public E elem() {
        if (endpos()) {
            throw new NoSuchElementException("Already at the end of this List");
        }
        return pos.next.o;
    }

    /**
     * Inserts <code>o</code> in this List. It will be placed before the actual
     * element. After insertion the inserted element will become the actual
     * element.
     *
     * @param x the element to be inserted
     */
    public void add(E x) {
        MyEntry<E> newone = new MyEntry<E>(x, pos.next);

        pos.next = newone;
    }

    /**
     * Deletes the actual element of this List. The element after the actual
     * element will become the new actual element.
     *
     * @throws NoSuchElementException if the last Entry of this List already has been reached.
     */
    public void delete() {
        if (endpos()) {
            throw new NoSuchElementException("Already at the end of this List");
        }
        pos.next = pos.next.next;
    }

    @Override
    public Iterator<E> iterator() {
        return new Iterator<E>() {
            private MyEntry<E> it = null;

            @Override
            public boolean hasNext() {
                return pos != null;
            }
            @Override
            public E next() {
                if (it==null)
                    it = begin;
                else
                    it = it.next;
                return it.o;
            }
            @Override
            public void remove() {
                throw new UnsupportedOperationException();
            }
        };
    }

}

我也已经尝试将Iterator实现到我的List并使用我的测试类

进行测试

public class MyListTest {

@Test
public void test() {

    MyList list = new MyList();

    list.add("a");
    list.add("b");
    list.add("c");

    while(list.iterator().hasNext()==true) {
        System.out.println(list);
    }

    list.iterator().remove();

    while(list.iterator().hasNext()==true) {
        System.out.println(list);
    }
}

}

但输出循环一个c，甚至没有删除一个条目。

我现在停留在快速失败迭代器的正确实现上，它可以遍历MyList并删除Entrys。因为我无法将其分解为单个问题，所以当我尝试实现迭代器时，我列出了一些问题

• Iterator应该在MyList类中实现还是应该在自己的类中实现？
• 如何让Iterator像advance（）方法一样推进MyList？
• 测试类中的while循环是否方便，还是应该使用其他方法？