Java 8 Streams是否可以对集合中的项目进行操作，然后将其删除？ [英] Can Java 8 Streams operate on an item in a collection, and then remove it?

问题描述

像大家一样，我仍然在学习新的Java 8 Streams API的复杂性（和爱他们）。我有一个关于流的使用问题。我将提供一个简化的例子。

Like just about everyone, I'm still learning the intricacies (and loving them) of the new Java 8 Streams API. I have a question concerning usage of streams. I'll provide a simplified example.

Java Streams允许我们使用 Collection c $ c> stream（）方法接收其所有元素的流。在其中，有一些有用的方法，如 filter（）， map（）和 forEach（），它允许我们对内容使用lambda操作。

Java Streams allows us to take a Collection, and use the stream() method on it to receive a stream of all of its elements. Within it, there are a number of useful methods, such as filter(), map(), and forEach(), which allow us to use lambda operations on the contents.

我有类似这样的代码简化）：

I have code that looks something like this (simplified):

set.stream().filter(item -> item.qualify())
    .map(item -> (Qualifier)item).forEach(item -> item.operate());
set.removeIf(item -> item.qualify());

这个想法是获取集合中所有匹配某个限定符的项目的映射，然后通过它们进行操作。操作后，它们没有进一步的用途，应该从原始集中删除。代码运行良好，但我不能动摇的感觉，在 Stream 中有一个操作，可以在一行中为我做这个。

The idea is to get a mapping of all items in the set, which match a certain qualifier, and then operate through them. After the operation, they serve no further purpose, and should be removed from the original set. The code works well, but I can't shake the feeling that there's an operation in Stream that could do this for me, in a single line.

如果是在Javadocs，我可能会忽略它。

If it's in the Javadocs, I may be overlooking it.

有谁更熟悉API看到这样？ p>

Does anyone more familiar with the API see something like that?

推荐答案

您可以这样做：

set.removeIf(item -> {
    if (!item.qualify())
        return false;
    item.operate();
    return true;
});

如果 item.operate（） true 您可以非常简洁。

If item.operate() always returns true you can do it very succinctly.

set.removeIf(item -> item.qualify() && item.operate());

但是，我不喜欢这些方法，因为它不是立即清楚发生了什么。就我个人而言，我会继续使用来替换循环和迭代器。

However, I don't like these approaches as it is not immediately clear what is going on. Personally, I would continue to use a for loop and an Iterator for this.

for (Iterator<Item> i = set.iterator(); i.hasNext();) {
    Item item = i.next();
    if (item.qualify()) {
        item.operate();
        i.remove();
    }
}

这篇关于Java 8 Streams是否可以对集合中的项目进行操作，然后将其删除？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！