链表栈

package fzu.com;

import java.util.Iterator;

//链表栈
public class LinkStack<Item> implements Iterable<Item> {

    private Node first;
    private int N;
    private class Node{
        Item item;
        Node next;
    }

    public boolean isEmpty(){
        return N == 0;
    }

    public int size(){
        return N;
    }

    public void push(Item item){
        Node oldFirst = first;
        first = new Node();
        first.item = item;
        first.next = oldFirst;
        N++;
    }

    public Item pop(){
        Item item = first.item;
        first = first.next;
        N--;
        return item;
    }

    @Override
    public Iterator<Item> iterator() {
        return new MyIterator();
    }

    private class MyIterator implements Iterator<Item>{

        private Node current = first;

        @Override
        public boolean hasNext() {
            return current != null;
        }

        @Override
        public Item next() {
            Item item = current.item;
            current = current.next;
            return item;
        }

        @Override
        public void remove() {

        }
    }

    public static void main(String[] args) {
        LinkStack<Integer> stack = new LinkStack<Integer>();
        stack.push(1);
        stack.push(2);
        stack.push(3);
        for (Integer a : stack){
            System.out.println(a);
        }
    }
}