使用Java 8 JDK將Iterable轉換爲Stream

本文翻譯自：Convert Iterable to Stream using Java 8 JDK

I have an interface which returns java.lang.Iterable<T> . 我有一個返回java.lang.Iterable<T>的接口。

I would like to manipulate that result using the Java 8 Stream API. 我想使用Java 8 Stream API處理該結果。

However Iterable can't "stream". 但是Iterable無法“流式傳輸”。

Any idea how to use the Iterable as a Stream without converting it to List? 任何想法如何將Iterable用作流而不轉換爲List？

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#1樓

參考：https://stackoom.com/question/1cPoz/使用Java-JDK將Iterable轉換爲Stream

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#2樓

You can easily create a Stream out of an Iterable or Iterator : 您可以使用Iterable或Iterator輕鬆創建Stream ：

public static <T> Stream<T> stream(Iterable<T> iterable) {
    return StreamSupport.stream(
        Spliterators.spliteratorUnknownSize(
            iterable.iterator(),
            Spliterator.ORDERED
        ),
        false
    );
}

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#3樓

There's a much better answer than using spliteratorUnknownSize directly, which is both easier and gets a better result. spliteratorUnknownSize直接使用spliteratorUnknownSize相比，有一個更好的答案，這既簡單又得到更好的結果。 Iterable has a spliterator() method, so you should just use that to get your spliterator. Iterable具有spliterator()方法，因此您應該使用該方法來獲取您的spliterator。 In the worst case, it's the same code (the default implementation uses spliteratorUnknownSize ), but in the more common case, where your Iterable is already a collection, you'll get a better spliterator, and therefore better stream performance (maybe even good parallelism). 在最壞的情況下，它是相同的代碼（默認實現使用spliteratorUnknownSize ），但是在更常見的情況下，如果您的Iterable已經是一個集合，您將獲得更好的分離器，從而獲得更好的流性能（甚至可能具有良好的並行性） ）。 It's also less code: 它的代碼也更少：

StreamSupport.stream(iterable.spliterator(), false)
             .filter(...)
             .moreStreamOps(...);

As you can see, getting a stream from an Iterable (see also this question ) is not very painful. 如您所見，從Iterable獲得流（也請參見此問題 ）不是很痛苦。

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#4樓

我想建議使用JOOL庫，它在Seq.seq（iterable）調用後隱藏了分隔符魔術，並且還提供了許多其他有用的功能。

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#5樓

I've created this class: 我創建了此類：

public class Streams {
    /**
     * Converts Iterable to stream
     */
    public static <T> Stream<T>  streamOf(final Iterable<T> iterable) {
        return toStream(iterable, false);
    }

    /**
     * Converts Iterable to parallel stream
     */
    public static <T> Stream<T> parallelStreamOf(final Iterable<T> iterable) {
        return toStream(iterable, true);
    }

    private static <T> Stream<T> toStream(final Iterable<T> iterable, final boolean isParallel) {
        return StreamSupport.stream(iterable.spliterator(), isParallel);
    }
}

I think it's perfectly readable because you don't have to think about spliterators and booleans (isParallel). 我認爲它是完全可讀的，因爲您不必考慮分隔符和布爾值（isParallel）。

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#6樓

如果您可以使用Guava庫（從21版開始），則可以使用

Streams.stream(iterable)