栈——java实现

定义

栈是一种后进先出的数据结构，即Last in first out,故又称LIFO表。栈只在表的一端进行插入（push）和删除（pop）操作，允许插入和删除的一端称为栈顶，

另一端则为栈底。

结构

如下图：

实现

栈的链表实现

使用单链表实现栈，代码如下：

package com.lemon.stack;/** * this class using list realize the stack of data structure * @author yanan * @param <T> */public class MyStack<T> {public static class Node<T>{private T value;private Node<T> next;public Node(T value, Node<T> next) {this.value = value;this.next = next;}}public MyStack(){this.topOfStack=new Node<T>(null, null);}private int size;private Node<T> topOfStack;/** * remove an element which is at the top of stack * @return */public T pop(){T t = topOfStack.value;  topOfStack = topOfStack.next;size--;return t; }/** * put the element to the end of stack * @param object */public void push(T object){Node<T> node=new Node<T>(object,null);node.next=topOfStack;topOfStack=node;size++;}/** * check whether current stack is null or not * @return */public boolean isEmpty(){return size==0;}/** * return an element which is at the top of stack * @return */public T peek(){return topOfStack.value;}public static void main(String[] args) {MyStack<String> stack=new MyStack<String>();stack.push("a");stack.push("b");stack.push("c");System.out.println(stack.pop());System.out.println(stack.size);System.out.println(stack.peek());}}

栈的数组实现

package com.lemon;/** * 栈的数组实现 * @author andy * */public class MyStack<T> {private static final int INIT_SIZE=5;Object[] data;int size=0;public MyStack(){data=new Object[INIT_SIZE];}public void push(Object obj){if(size>data.length){throw new ArrayIndexOutOfBoundsException();}if(size==data.length){//当栈满时,其容量扩大两倍.Object[] newData=new Object[data.length*2];for(int i=0;i<data.length;i++){newData[i]=data[i];}data=newData;}data[size]=obj;size++;}public Object peek(){Object obj=data[size-1==0?0:size-1];return obj;}public Object pop(){int index=size-1==0?0:size-1;Object obj=data[index];data[index]=null;size--;return obj;}public boolean isEmpty(){return size<=0;}public static void main(String[] args) {MyStack<String> stack=new MyStack<String>();stack.push("a");stack.push("2");stack.push("3");stack.push("c");stack.push("5");stack.push("6");System.out.println(stack.peek());while(!stack.isEmpty()){System.out.println(stack.pop());}}}