将 Iterable 转换为 Collection 的简单方法 [英] Easy way to convert Iterable to Collection

问题描述

在我的应用程序中，我使用了 3rd 方库(准确地说是 Spring Data for MongoDB).

In my application I use 3rd party library (Spring Data for MongoDB to be exact).

这个库的方法返回Iterable，而我的其余代码需要Collection.

Methods of this library return Iterable<T>, while the rest of my code expects Collection<T>.

是否有任何实用方法可以让我快速将一种转换为另一种?我想避免在我的代码中为这么简单的事情创建一堆 foreach 循环.

Is there any utility method somewhere that will let me quickly convert one to the other? I would like to avoid creating a bunch of foreach loops in my code for such a simple thing.

推荐答案

使用 Guava 你可以使用 Lists.newArrayList(Iterable) 或 Sets.newHashSet(Iterable)，以及其他类似的方法.这当然会将所有元素复制到内存中.如果这是不可接受的，我认为与这些一起使用的代码应该采用 Iterable 而不是 Collection.Guava 也恰好提供了方便的方法，可以使用 Iterable(例如 Iterables.isEmpty(Iterable) 或Iterables.contains(Iterable, Object))，但性能影响更明显.

With Guava you can use Lists.newArrayList(Iterable) or Sets.newHashSet(Iterable), among other similar methods. This will of course copy all the elements in to memory. If that isn't acceptable, I think your code that works with these ought to take Iterable rather than Collection. Guava also happens to provide convenient methods for doing things you can do on a Collection using an Iterable (such as Iterables.isEmpty(Iterable) or Iterables.contains(Iterable, Object)), but the performance implications are more obvious.

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