经常看到的观点：
ArrayList查询快，增删改慢
LinkedList查询慢，增删改快
先看下面demo代码：
 

  public static void main(String[] args) {
        int n = 1000;
        int insertIndex = n;
        for (int i = 0; i < 1; i++) {
           //randomArray生面随机数组，这里意思是1000个随机数
            int[] array = randomArray(n);
            List<Integer> list1 = 
        Arrays.stream(array).boxed().collect(Collectors.toList());
            LinkedList<Integer> list2 = new LinkedList<>(list1);
            addFirst(list1,list2);
            addMiddle(list1, list2, n / 2);
            addLast(list1,list2);
            arrayListSize((ArrayList<Integer>) list1);
            linkedListSize(list2);
        }
    }
 private static void addMiddle(List<Integer> list1, LinkedList<Integer> list2, int mid) {
        StopWatch sw = new StopWatch();
        sw.start("ArrayList");
        list1.add(mid, 100);
        sw.stop();

        sw.start("LinkedList");
        list2.add(mid, 100);
        sw.stop();

        System.out.println(sw.prettyPrint());
    }

    private static void addFirst(List<Integer> list1, LinkedList<Integer> list2) {
        StopWatch sw = new StopWatch();
        sw.start("ArrayList");
        list1.add(0, 100);
        sw.stop();

        sw.start("LinkedList");
        list2.addFirst(100);
        sw.stop();

        System.out.println(sw.prettyPrint());
    }

    private static void addLast(List<Integer> list1, LinkedList<Integer> list2) {
        StopWatch sw = new StopWatch();
        sw.start("ArrayList");
        list1.add(100);
        sw.stop();

        sw.start("LinkedList");
        list2.add(100);
        sw.stop();

        System.out.println(sw.prettyPrint());
    }

执行往头部addFirst插入的运行截图如下：LinkedList的效率比ArrayList的效率好很多
 

Connected to the target VM, address: '127.0.0.1:59369', transport: 'socket'
StopWatch '': running time = 81898 ns
---------------------------------------------
ns         %     Task name
---------------------------------------------
000073599  090%  ArrayList
000008299  010%  LinkedList

Disconnected from the target VM, address: '127.0.0.1:59369', transport: 'socket'

Process finished with exit code 0

执行往中间addMiddle插入的运行结果:
 

Connected to the target VM, address: '127.0.0.1:62319', transport: 'socket'
StopWatch '': running time = 5230109099 ns
---------------------------------------------
ns         %     Task name
---------------------------------------------
1677949199  032%  ArrayList
3552159900  068%  LinkedList

往最后插入运行截图：
 

ns         %     Task name
---------------------------------------------
000027600  087%  ArrayList
000004200  013%  LinkedList

往中间插入元素的时候，LinkedList并不是很快，因为LinkedList也要循环找到中间那个位置在插入。头和尾插入挺快的