ArrayList.ListIterator（INT指数）与ArrayList.get（INT指数） [英] ArrayList.ListIterator(int index) vs ArrayList.get(int index)

问题描述

我想知道用ArrayList.ListIterator时对性能的影响会是什么？（INT指数 - 1），然后对比使用ArrayList.get（INT指数）it.next（）

I was wondering what the performance impact would be when using ArrayList.ListIterator(int index - 1), then it.next() in contrast to using ArrayList.get(int index)?

推荐答案

为什么看实现...

public ListIterator<E> listIterator(final int index) {
if (index<0 || index>size())
  throw new IndexOutOfBoundsException("Index: "+index);

return new ListItr(index);
}

与

private class ListItr extends Itr implements ListIterator<E> {
ListItr(int index) {
    cursor = index;
}

// [...]

和

public E next() {
        checkForComodification();
    try {
    E next = get(cursor);
    lastRet = cursor++;
    return next;
    } catch (IndexOutOfBoundsException e) {
    checkForComodification();
    throw new NoSuchElementException();
    }
}

2：List.get（INT）

public E get(int index) {
RangeCheck(index);

return (E) elementData[index];
}

应该是相当明显的，哪一个是速度更快。有关性能影响的细节，我将与麦克同意。简介吧。不管是什么原因，你想使用这种独特的访问方法只访问一个项目（？）

Should be quite obvious, which one is faster. For details about performance impacts, I will have to agree with Mike. Profile it. Whatever the reason is, you'd like to use such a distinct access method just to access one item (?)

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