ArrayList与LinkedList性能差别

1、             ArrayList和LinkedList插入元素性能差别

ArrayList内部使用数组存储，针对这一性质，在数组最后插入元素较快，在数组中间插入元素较慢，因为插入位置之后的元素要后移。而LinkedList在哪个位置插入都比较快，当然在LinkedList中间位置插入时，也涉及到遍历时间，但是该时间比较短。下面是测试。

测试一：插入到最后位置，性能差别不大

package com.pcitc.pattern.collection;

import java.util.AbstractList;

import java.util.ArrayList;

import java.util.Date;

import java.util.Iterator;

import java.util.LinkedList;

import java.util.List;

public class ArryListClient {

/**

 * @param args

 */

public static void main(String[] args) {

           List<UserBean> list = new ArrayList<UserBean>();

           List<UserBean> linkedlist = new LinkedList<UserBean>();

          

           int count = 100000;

    System.out.println("run...");

           UserBean ub = null;

        long i1 = System.currentTimeMillis();

        for(int i = 0;i<count;i++){

        ub = new UserBean(""+i,i,"ddd"+i);

        list.add(i,ub);

        }

        long i2 = System.currentTimeMillis();

        System.out.println("增加元素，Arraylist耗时:" + (i2-i1));

      

        long i3 = System.currentTimeMillis();

        for(int i = 0;i<count;i++){

        ub = new UserBean(""+i,i,"ddd"+i);

        linkedlist.add(0,ub);

        }

        long i4 = System.currentTimeMillis();

        System.out.println("增加元素，linkedlist耗时:" + (i4-i3));   

    

        list.clear();

        linkedlist.clear();

        list = null;

        linkedlist = null;

}

性能一运行结果：

run...

增加元素，Arraylist耗时:219

增加元素，linkedlist耗时:141

测试二：插入到首位置，性能差别大

package com.pcitc.pattern.collection;

import java.util.AbstractList;

import java.util.ArrayList;

import java.util.Date;

import java.util.Iterator;

import java.util.LinkedList;

import java.util.List;

public class ArryListClient {

/**

 * @param args

 */

public static void main(String[] args) {

           List<UserBean> list = new ArrayList<UserBean>();

           List<UserBean> linkedlist = new LinkedList<UserBean>();

          

           int count = 100000;

    System.out.println("run...");

           UserBean ub = null;

        long i1 = System.currentTimeMillis();

        for(int i = 0;i<count;i++){

        ub = new UserBean(""+i,i,"ddd"+i);

        list.add(0,ub);

        }

        long i2 = System.currentTimeMillis();

        System.out.println("增加元素，Arraylist耗时:" + (i2-i1));

      

        long i3 = System.currentTimeMillis();

        for(int i = 0;i<count;i++){

        ub = new UserBean(""+i,i,"ddd"+i);

        linkedlist.add(0,ub);

        }

        long i4 = System.currentTimeMillis();

        System.out.println("增加元素，linkedlist耗时:" + (i4-i3));   

    

        list.clear();

        linkedlist.clear();

        list = null;

        linkedlist = null;

}

}

性能二运行结果：性能差36倍之多

run...

增加元素，Arraylist耗时:6250

增加元素，linkedlist耗时:234