Java8内部迭代 [英] Java8 internal iteration

问题描述

java8 forEach方法是否真的使用迭代器？我把它谷歌到骨头，找不到它。只是它会以相同的顺序迭代数据。

Does java8 forEach method use an iterator or not really? I google it to the bone, could not find it precisely. Only the fact that it will iterate in the same order the data are.

任何提示？

推荐答案

Iterable＃forEach的默认实现基于迭代器。

The default implementation of Iterable#forEach is based on a iterator.

    default void forEach(Consumer<? super T> action) {
        Objects.requireNonNull(action);
        for (T t : this) {
            action.accept(t);
        }
    }

但是在ArrayList中重写了这个，而不是使用迭代器，它在其内部数组上使用for循环

But in ArrayList is overridden to this, and not uses the iterator, it uses a for loop over its internal array

    @Override
    public void forEach(Consumer<? super E> action) {
        Objects.requireNonNull(action);
        final int expectedModCount = modCount;
        @SuppressWarnings("unchecked")
        final E[] elementData = (E[]) this.elementData;
        final int size = this.size;
        for (int i=0; modCount == expectedModCount && i < size; i++) {
            action.accept(elementData[i]);
        }
        if (modCount != expectedModCount) {
            throw new ConcurrentModificationException();
        }
    }

所以这取决于它的实现。

So it depends of its implementation.

无论如何，由于此方法是在Iterable接口中声明的，因此所有迭代都使用此方法。

Anyway, since this method is declared in Iterable interface, all iterables has this method.

这篇关于Java8内部迭代的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！