java实现一个栈

 

/**
 * @Project:      Test     
 * @File:         org.coffeesweet.test01.Test19.java
 * @Author:       coffeesweet
 * @Date:         2011-6-7
 * @Description:  2011 coffeesweet Inc. All rights reserved.
 */
package org.coffeesweet.test01;

import java.util.LinkedList;

/**
 * @author coffeesweet
 *
 */
public class Test19 {

	public static void main(String[] args){
		Long[] numList = new Long[]{1L,5L,3L,2L,1L,5L,7L,6L,7L,8L,-1L,-5L,2L,7L,2L,3L,5L,9L,9L};
		Test19 t19 = new Test19();
		MaxNumStack mns = t19.new MaxNumStack();
		for(int i=0;i<numList.length;i++){
			mns.push(numList[i]);
		}
		System.out.println(mns.pop());
		System.out.println(mns.pop());
		System.out.println(mns.top());
		System.out.println(mns.getMaxNum());
	}
	
	private class MaxNumStack{
		
		private LinkedList<Long> stackList = new LinkedList<Long>();
		private LinkedList<Long> maxNumList = new LinkedList<Long>();
		
		public void push(Long num){
			stackList.addLast(num);
			if(maxNumList.isEmpty()||(maxNumList.getLast().compareTo(num)<1)){
				maxNumList.addLast(num);
			}
		}
		
		public Long pop(){
			if(stackList.isEmpty())return null;
			if((maxNumList.getLast().compareTo(stackList.getLast())<1))maxNumList.removeLast();
			return stackList.removeLast();
		}
		
		public Long top(){
			return stackList.getLast();
		}
		
		public boolean isEmpty(){
			return stackList.isEmpty();
		}
		
		public Long getMaxNum(){
			if(maxNumList.isEmpty())return null;
			return maxNumList.getLast();
		}
	}
}