栈stack的Demo

基于java实现的stack

package com.test.stack;

import java.util.Iterator;

public class StackDemo implements Iterable{

    private Node head;
    private int N;

    public static void main(String[] args) {
        StackDemo stackDemo = new StackDemo<>();
        stackDemo.push("a");
        stackDemo.push("b");
        stackDemo.push("c");
        stackDemo.push("d");
        for (Object item : stackDemo) {
            System.out.println(item);
        }
        System.out.println("----------------");
        System.out.println(stackDemo.pop());
        System.out.println("----------------------");
        for (Object item : stackDemo) {
            System.out.println(item);
        }
    }

    public StackDemo(){
        head = new Node(null,null);
        N = 0;
    }

    //栈是否为空
    public boolean isEmpty(){
        return N == 0;
    }

    //数据压入栈
    public void push(T item){
        Node oldNode = head.next;
        Node newNode = new Node(item,oldNode);
        head.next = newNode;
        N++;
    }

    //弹出栈顶数据
    public T pop(){
        Node oldNode = head.next;
        Node oldNodeNext = oldNode.next;
        head.next = oldNodeNext;
        N--;
        return oldNode.item;
    }

    //获取栈的长度
    public int size(){
        return N;
    }

    //内部类，实现遍历
    private class SIterator implements Iterator{
        private Node n = head;
        @Override
        public boolean hasNext() {
            return n.next!=null;
        }

        @Override
        public T next() {
            Node node = n.next;
            n = n.next;
            return node.item;
        }
    }

    @Override
    public Iterator iterator() {
        return new SIterator();
    }

    private class Node{
        public T item;
        public Node next;
        public Node(T item,Node next){
            this.item = item;
            this.next = next;
        }
    }
}