用数组和链表两种方式实现栈

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1.数组方式

import java.util.Arrays;class MyStack<E>{private Object[] stack;int size;//数组中存储元素的个数public MyStack() {stack=new Object[10];//初始长度为10}//判断堆中元素是否为空public boolean isEmpty(){return size==0;}//取出栈顶元素public E peek(){if(isEmpty()){return null;}return (E)stack[size-1];}//出栈操作public E pop(){E e=peek();stack[size-1]=null;size--;return e;}//入栈操作public E push(E item){ensureCapacity(size+1);//检查容量stack[size++]=item;return item;}//判断数组容器是否已满，若已满则扩充数组空间private void ensureCapacity(int size){int len=stack.length;if(size>len){//数组已满int newLen=10;//每次数组扩充的容量stack=Arrays.copyOf(stack, newLen);}}}public class Main2 {public static void main(String[] args) {MyStack<Integer> s=new MyStack<Integer>();s.push(1);s.push(2);System.out.println("栈中元素个数:"+s.size);System.out.println("栈顶元素为："+s.pop());}}

2.链表方式

class Node<E>{Node <E>next=null;E data;public Node(E data){this.data=data;}}public class Stack<E> {Node<E> top=null;public boolean isEmpty(){return top==null;}public void push(E data){Node<E> newNode=new Node<E>(data);newNode.next=top;top=newNode;}public E pop(){if(this.isEmpty()){return null;}E data=top.data;top=top.next;return data;}public E peek(){if(this.isEmpty()){return null;}return top.data;}public static void main(String[] args) {Stack<Integer> s=new Stack<Integer>();s.push(1);s.push(2);System.out.println("栈顶元素为："+s.pop());}}

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