先说一下关于LinkedList插入 遍历使用时间的情况

电脑配置： image.png
image.png

使用for循环遍历

10w的数据量

  public static void main(String[] args) {
        LinkedList linkedList = new LinkedList();


        Long startTime = System.currentTimeMillis();

        for (int i = 0 ; i <100000;i++) {

            linkedList.add(i);
        }


        Long endTime = System.currentTimeMillis();

        System.out.println("插入完成,耗时："+(endTime-startTime)/1000.0+"s");

        startTime= System.currentTimeMillis();


        for (int i = 0 ; i<100000;i++) {
            linkedList.get(i);
        }

        endTime = System.currentTimeMillis();

        System.out.println("遍历完成,耗时："+(endTime-startTime)/1000.0+"s");



    }





插入完成,耗时：0.007s
遍历完成,耗时：5.69s
Heap
 PSYoungGen      total 76288K, used 14419K [0x000000076b100000, 0x0000000770600000, 0x00000007c0000000)
  eden space 65536K, 22% used [0x000000076b100000,0x000000076bf14e68,0x000000076f100000)
  from space 10752K, 0% used [0x000000076fb80000,0x000000076fb80000,0x0000000770600000)
  to   space 10752K, 0% used [0x000000076f100000,0x000000076f100000,0x000000076fb80000)
 ParOldGen       total 175104K, used 0K [0x00000006c1200000, 0x00000006cbd00000, 0x000000076b100000)
  object space 175104K, 0% used [0x00000006c1200000,0x00000006c1200000,0x00000006cbd00000)
 Metaspace       used 3981K, capacity 4572K, committed 4864K, reserved 1056768K
  class space    used 435K, capacity 460K, committed 512K, reserved 1048576K

1百万数据量

 public static void main(String[] args) {
        LinkedList linkedList = new LinkedList();


        Long startTime = System.currentTimeMillis();
        
        for (int i = 0 ; i <1000000;i++) {

            linkedList.add(i);
        }


        Long endTime = System.currentTimeMillis();
        
        System.out.println("插入完成,耗时："+(endTime-startTime)/1000.0+"s");

        startTime= System.currentTimeMillis();


        for (int i = 0 ; i<1000000;i++) {
            linkedList.get(i);
        }

        endTime = System.currentTimeMillis();
        
        System.out.println("遍历完成,耗时："+(endTime-startTime)/1000.0+"s");



    }





插入完成,耗时：0.027s
遍历完成,耗时：701.095s
Heap
 PSYoungGen      total 76288K, used 49809K [0x000000076b100000, 0x0000000770600000, 0x00000007c0000000)
  eden space 65536K, 76% used [0x000000076b100000,0x000000076e1a45d0,0x000000076f100000)
  from space 10752K, 0% used [0x000000076fb80000,0x000000076fb80000,0x0000000770600000)
  to   space 10752K, 0% used [0x000000076f100000,0x000000076f100000,0x000000076fb80000)
 ParOldGen       total 175104K, used 0K [0x00000006c1200000, 0x00000006cbd00000, 0x000000076b100000)
  object space 175104K, 0% used [0x00000006c1200000,0x00000006c1200000,0x00000006cbd00000)
 Metaspace       used 3981K, capacity 4572K, committed 4864K, reserved 1056768K
  class space    used 435K, capacity 460K, committed 512K, reserved 1048576K

可以看出数据量小的情况下 for循环get遍历 的时候10万数据要5秒 数据量大的情况下 100W数据要701秒

使用迭代器

10W数据量

 public static void main(String[] args) {
        LinkedList linkedList = new LinkedList();


        Long startTime = System.currentTimeMillis();

        for (int i = 0 ; i <100000;i++) {

            linkedList.add(i);
        }


        Long endTime = System.currentTimeMillis();

        System.out.println("插入完成,耗时："+(endTime-startTime)/1000.0+"s");

        startTime= System.currentTimeMillis();



        Iterator iterator = linkedList.iterator();

        while (iterator.hasNext()) {

            iterator.next() ;

        }
        endTime = System.currentTimeMillis();

        System.out.println("遍历完成,耗时："+(endTime-startTime)/1000.0+"s");

  插入完成,耗时：0.008s
遍历完成,耗时：0.002s
Heap
 PSYoungGen      total 76288K, used 10487K [0x000000076b100000, 0x0000000770600000, 0x00000007c0000000)
  eden space 65536K, 16% used [0x000000076b100000,0x000000076bb3dd68,0x000000076f100000)
  from space 10752K, 0% used [0x000000076fb80000,0x000000076fb80000,0x0000000770600000)
  to   space 10752K, 0% used [0x000000076f100000,0x000000076f100000,0x000000076fb80000)
 ParOldGen       total 175104K, used 0K [0x00000006c1200000, 0x00000006cbd00000, 0x000000076b100000)
  object space 175104K, 0% used [0x00000006c1200000,0x00000006c1200000,0x00000006cbd00000)
 Metaspace       used 3481K, capacity 4500K, committed 4864K, reserved 1056768K
  class space    used 378K, capacity 388K, committed 512K, reserved 1048576K

    }

100W数据量

  public static void main(String[] args) {
        LinkedList linkedList = new LinkedList();


        Long startTime = System.currentTimeMillis();

        for (int i = 0 ; i <1000000;i++) {

            linkedList.add(i);
        }


        Long endTime = System.currentTimeMillis();

        System.out.println("插入完成,耗时："+(endTime-startTime)/1000.0+"s");

        startTime= System.currentTimeMillis();



        Iterator iterator = linkedList.iterator();

        while (iterator.hasNext()) {

            iterator.next() ;

        }
        endTime = System.currentTimeMillis();

        System.out.println("遍历完成,耗时："+(endTime-startTime)/1000.0+"s");



    }


插入完成,耗时：0.029s
遍历完成,耗时：0.011s
Heap
 PSYoungGen      total 76288K, used 45877K [0x000000076b100000, 0x0000000770600000, 0x00000007c0000000)
  eden space 65536K, 70% used [0x000000076b100000,0x000000076ddcd4f8,0x000000076f100000)
  from space 10752K, 0% used [0x000000076fb80000,0x000000076fb80000,0x0000000770600000)
  to   space 10752K, 0% used [0x000000076f100000,0x000000076f100000,0x000000076fb80000)
 ParOldGen       total 175104K, used 0K [0x00000006c1200000, 0x00000006cbd00000, 0x000000076b100000)
  object space 175104K, 0% used [0x00000006c1200000,0x00000006c1200000,0x00000006cbd00000)
 Metaspace       used 3485K, capacity 4500K, committed 4864K, reserved 1056768K
  class space    used 378K, capacity 388K, committed 512K, reserved 1048576K