List、Vector插入性能比较

从学习java开始就知道vector使用synchronized对方法进行加锁,所以线程安全但性能较低,但随着java的对于锁的优化,现在似乎已经不是这样了,下面开始验证一下

package com.kevindai.jdk8;

import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Vector;
import java.util.concurrent.CountDownLatch;

/**
 * Create by daiwenkai
 * on 2018/2/8 上午11:49
 */
public class TestListVector {
    public static void main(String[] args) throws Exception {
        List arrayList = new ArrayList<>();
        List linkedList = new LinkedList<>();
        Vector vector = new Vector<>();


        CountDownLatch countDownLatch1 = new CountDownLatch(50000);
        CountDownLatch countDownLatch2 = new CountDownLatch(50000);
        CountDownLatch countDownLatch3 = new CountDownLatch(50000);

        Long t1 = 0l;
        Long t2 = 0l;
        Long t3 = 0l;

        Long s1 = System.currentTimeMillis();
        for (int i = 0; i < 50000; i++) {
            Thread thread = new Thread(() -> {
                arrayList.add(System.currentTimeMillis());
                countDownLatch1.countDown();

            });
            thread.start();
        }
        for (int i = 0; i < arrayList.size(); i++) {
            arrayList.get(i);
        }
        countDownLatch1.await();
        Long e1 =System.currentTimeMillis();
        t1 = e1 - s1;


        Long s2 = System.currentTimeMillis();
        for (int i = 0; i < 50000; i++) {
            Thread thread = new Thread(() -> {
                linkedList.add(System.currentTimeMillis());
                countDownLatch2.countDown();

            });
            thread.start();
        }
        countDownLatch2.await();
        //这段代码有时候会报空指针异常,原因未知,很奇怪
        for (int i = 0; i < linkedList.size(); i++) {
            linkedList.get(i);
        }
        //这段代码有时候会报空指针异常,原因未知,很奇怪
        Long e2 =System.currentTimeMillis();
        t2 = e2 - s2;

        Long s3 = System.currentTimeMillis();
        for (int i = 0; i < 50000; i++) {
            Thread thread = new Thread(() -> {
                vector.add(System.currentTimeMillis());
                countDownLatch3.countDown();

            });
            thread.start();
        }
        countDownLatch3.await();
        for (int i = 0; i < vector.size(); i++) {
            vector.get(i);
        }
        Long e3 =System.currentTimeMillis();
        t3 = e3 - s3;


        System.out.println("arrayList:" + arrayList.size() + "," + t1);
        System.out.println("linkedList:" + linkedList.size() + "," + t2);
        System.out.println("vector:" + vector.size() + "," + t3);
    }
}

上面这个demo是用多线程分别往ArrayList、LinkedList、Vector中插入50000个元素,然后读取出来,结果如下图

可以看到vector的速度反而最快

所以啊,要保持不断的学习,跟上技术的更新啊!