list.clear（）VS名单=新的ArrayList＆LT;整数GT;（）; [英] list.clear() vs list = new ArrayList<Integer>();

问题描述

其中的2个选项一个是更好，更快地清除ArrayList和

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

list.clear() 

或

list = new ArrayList<Integer>();

它发生，我必须这样做，在随机时间，清除所有从我的ArrayList我条目，并没有办法知道有多少新的项目会出现在未来，有可能是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

这是很难知道没有一个标杆，但如果你有很多的项目在ArrayList和平均规模较低，这可能会更快做出新ArrayList的。

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.

<一个href=\"http://www.docjar.com/html/api/java/util/ArrayList.java.html\">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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