【Android】ArrayList、LinkedList

  • ArrayList
    • 基于数组实现,查找快:o(1),增删慢:o(n)
    • 初始容量为10,扩容通过 System.arrayCopy 方法
  • LinkedList
    • 基于双向链表实现,查找慢:o(n),增删快:o(1)
    • 封装了队列和栈的调用

数组与链表有什么不同?

 

(双向)链表的优缺点?为什么查找慢、增删快?

 

数组的优缺点?为什么查找快、增删慢?

 


关于ArrayList与LinkedList的实现区别分析:

public class LinkedList
    extends AbstractSequentialList
    implements List, Deque, Cloneable, java.io.Serializable
{}
public abstract class AbstractSequentialList extends AbstractList 
{}


public class ArrayList extends AbstractList
        implements List, RandomAccess, Cloneable, java.io.Serializable
{}

AbstractSequentialList有什么用?

 


ArrayList实现的RandomAccess接口有什么用?

Collections是集合的一个工具类,我们看一下Collections源码中的二分搜索方法。

    int binarySearch(List> list, T key) {
        if (list instanceof RandomAccess || list.size()
    int indexedBinarySearch(List> list, T key) {
        int low = 0;
        int high = list.size()-1;

        while (low <= high) {
            int mid = (low + high) >>> 1;
            Comparable midVal = list.get(mid);
            int cmp = midVal.compareTo(key);

            if (cmp < 0)
                low = mid + 1;
            else if (cmp > 0)
                high = mid - 1;
            else
                return mid; // key found
        }
        return -(low + 1);  // key not found
    }

    private static 
    int iteratorBinarySearch(List> list, T key)
    {
        int low = 0;
        int high = list.size()-1;
        ListIterator> i = list.listIterator();

        while (low <= high) {
            int mid = (low + high) >>> 1;
            Comparable midVal = get(i, mid);
            int cmp = midVal.compareTo(key);

            if (cmp < 0)
                low = mid + 1;
            else if (cmp > 0)
                high = mid - 1;
            else
                return mid; // key found
        }
        return -(low + 1);  // key not found
    }

这里是根据是否实现了RandomAccess接口来决定使用不同的方法,这两种方法有什么区别?

  • indexedBinarySearch使用的索引遍历(实现了RandomAccess接口的List >> ArrayList)
  • iteratorBinarySearch使用的是迭代器遍历( >> LinkedList)

为什么要使用不同的遍历方式?

  • ArrayList通过for遍历比通过iterator遍历要快(测试结果) 
  • LinkedList通过iterator遍历比通过for遍历要快(测试结果)

遍历速度为什么不一样?

https://mp.weixin.qq.com/s?src=11×tamp=1594897453&ver=2464&signature=NgWxHiHseXcv5rXCpg8gyYjYqB5G31y2VQpV*ZidT8uhRNGMJuSgTHO1bN*MIP7il6YOCmNmHpmA6moQhOV4aOMHXL*VzTBOVRF0LpXPhgZ6EtHDv9thI4fbt9VI1zm*&new=1

https://www.cnblogs.com/yeya/p/9950723.html


LinkedList实现的Deque接口有什么用?

 

 

 

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