list.clear() vs list = new ArrayList<Integer>(); [英] list.clear() vs list = new ArrayList&lt;Integer&gt;();

问题描述

这 2 个选项中哪个更好更快地清除 ArrayList，为什么?

Which one of the 2 options is better and faster to clear an ArrayList, and why?

list.clear() 

或

list = new ArrayList<Integer>();

碰巧我必须在随机时间清除我的 ArrayList 中的所有条目，我无法知道将来会有多少新条目，可能是 0 或 1000.哪种方法更快更好，为什么?

It happens that I have to, at random times, clear all entries from my ArrayList and I have no way to know how many new entries there will be in the future, there might be 0 or a 1000. Which method is faster and better, and why?

推荐答案

如果没有基准测试很难知道，但是如果您的 ArrayList 中有很多项并且平均大小较小，那么制作一个新的可能会更快数组列表.

It's hard to know without a benchmark, but if you have lots of items in your ArrayList and the average size is lower, it might be faster to make a new ArrayList.

http://www.docjar.com/html/api/java/util/ArrayList.java.html

public void clear() {
    modCount++;

    // Let gc do its work
    for (int i = 0; i < size; i++)
        elementData[i] = null;

    size = 0;
}

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