设计模式＝＝迭代器模式（Iterator）

/*
 * 迭代器模式（Iterator）
 *
 * 类似于集合中的Iterator，使用迭代器来统一不同集合对象的遍历方式，
 * 隐藏内部细节，用一个抽象迭代器，每个具体的集合类来实现特有的迭代器。
 */

package model;

public class TestIterator {
    public static void main(String[] args) {
        Stack s = new Stack();
        s.push("Liucy");
        s.push("Huxz");
        s.push("George");
        LinkedList l = new LinkedList();
        l.addFirst("Liucy");
        l.addFirst("Huxz");
        l.addFirst("George");
        print(l.iterator());
    }

    public static void print(Itr it) {
        while (it.hasNext()) {
            System.out.println(it.next());
        }
    }
}

interface Itr {
    boolean hasNext();

    Object next();
}

class Stack {
    Object[] os = new Object[10];
    int index = 0;

    private void expand() {
        Object[] os2 = new Object[os.length * 2];
        System.arraycopy(os, 0, os2, 0, os.length);
        os = os2;
    }

    public void push(Object o) {
        if (index == os.length)
            expand();
        os[index] = o;
        index++;
    }

    public Object pop() {
        index--;
        Object o = os[index];
        os[index] = null;
        return o;
    }

    private class StackItr implements Itr {
        int cursor = 0;

        public boolean hasNext() {
            return cursor < index;
        }

        public Object next() {
            return os[cursor++];
        }
    }

    public Itr iterator() {
        return new StackItr();
    }
}

class LinkedList {
    private class Node {
        Object o;
        Node next;

        public Node(Object o) {
            this.o = o;
        }

        public void setNext(Node next) {
            this.next = next;
        }

        public Node getNext() {
            return this.next;
        }
    }

    Node head;

    public void addFirst(Object o) {
        Node n = new Node(o);
        n.setNext(head);
        head = n;
    }

    public Object removeFirst() {
        Node n = head;
        head = head.getNext();
        return n.o;
    }

    class LinkedListItr implements Itr {
        Node currentNode = head;

        public boolean hasNext() {
            return this.currentNode != null;
        }

        public Object next() {
            Node n = currentNode;
            currentNode = currentNode.getNext();
            return n.o;
        }
    }

    public Itr iterator() {
        return new LinkedListItr();
    }
}