java基础之List遍历速度

一、对ArrayList与LinkedList分别使用10w次不同的方式进行遍历,试了三次,结果如下

arrayList:for:12
arrayList:for-earch:11
arrayList:forEach:167
arrayList:parallelStream().forEach:18
arrayList:stream().collect:14
linkedList:for:13081
linkedList:for-earch:10
linkedList:forEach:7
linkedList:parallelStream().forEach:8
linkedList:stream().collect:7

arrayList:for:14
arrayList:for-earch:24
arrayList:forEach:143
arrayList:parallelStream().forEach:16
arrayList:stream().collect:16
linkedList:for:11562
linkedList:for-earch:3
linkedList:forEach:6
linkedList:parallelStream().forEach:8
linkedList:stream().collect:6


arrayList:for:13
arrayList:for-earch:11
arrayList:forEach:120
arrayList:parallelStream().forEach:25
arrayList:stream().collect:18
linkedList:for:9482
linkedList:for-earch:6
linkedList:forEach:7
linkedList:parallelStream().forEach:8
linkedList:stream().collect:6

 

二、根据结果总结

使用ArrayList的时候,使用list.forEach()这个性能最差,差距性能比其他方式差10倍

使用LinkedList的时候,使用for(int i=0;i

 

三、测试代码

public class ForTestMain {

    public static void main(String[] args) {
        List arrayList=new ArrayList<>();
        List linkedList=new LinkedList<>();
        for(int i=0;i<100000;i++){
            arrayList.add(i);
            linkedList.add(i);
        }

        compare("arrayList",arrayList);
        compare("linkedList",linkedList);

    }

    public static void compare(String flag,List dataList){
        int size=dataList.size();
        long startTime=System.currentTimeMillis();
        for(int i=0;i{});

        finish=System.currentTimeMillis();
        System.out.println(flag+":forEach:"+(finish-startTime));

        startTime=System.currentTimeMillis();
        dataList.parallelStream().forEach(s->{});

        finish=System.currentTimeMillis();
        System.out.println(flag+":parallelStream().forEach:"+(finish-startTime));


        startTime=System.currentTimeMillis();
        dataList.stream().collect(Collectors.toList());
        finish=System.currentTimeMillis();
        System.out.println(flag+":stream().collect:"+(finish-startTime));
    }

}






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