您可以使用Eclipse Collections工厂:

Iterable<String> iterable = Arrays.asList("1", "2", "3");

MutableList<String> list = Lists.mutable.withAll(iterable);
MutableSet<String> set = Sets.mutable.withAll(iterable);
MutableSortedSet<String> sortedSet = SortedSets.mutable.withAll(iterable);
MutableBag<String> bag = Bags.mutable.withAll(iterable);
MutableSortedBag<String> sortedBag = SortedBags.mutable.withAll(iterable);

您还可以将Iterable转换为LazyIterable，并使用转换器方法或任何其他可用的api。

Iterable<String> iterable = Arrays.asList("1", "2", "3");
LazyIterable<String> lazy = LazyIterate.adapt(iterable);

MutableList<String> list = lazy.toList();
MutableSet<String> set = lazy.toSet();
MutableSortedSet<String> sortedSet = lazy.toSortedSet();
MutableBag<String> bag = lazy.toBag();
MutableSortedBag<String> sortedBag = lazy.toSortedBag();

以上所有可变类型都扩展了java.util.Collection。

注意:我是Eclipse Collections的提交者。

来自common -collections的IteratorUtils可能会有所帮助(尽管它们在最新的稳定版本3.2.1中不支持泛型):

@SuppressWarnings("unchecked")
Collection<Type> list = IteratorUtils.toList(iterable.iterator());

4.0版本(目前在SNAPSHOT中)支持泛型，您可以去掉@SuppressWarnings。

更新:检查IterableAsList从仙人掌。

我经常使用fluentiatable .from(myIterable). tolist()。

只要你调用contains, containsAll, equals, hashCode, remove, retainAll, size或toArray，你就必须遍历元素。

如果您偶尔只调用isEmpty或clear等方法，我认为您最好是惰性地创建集合。例如，你可以有一个支持数组列表来存储先前迭代的元素。

我不知道任何一个库中有这样的类，但是编写它应该是一个相当简单的练习。

两个评论

There is no need to convert Iterable to Collection to use foreach loop - Iterable may be used in such loop directly, there is no syntactical difference, so I hardly understand why the original question was asked at all. Suggested way to convert Iterable to Collection is unsafe (the same relates to CollectionUtils) - there is no guarantee that subsequent calls to the next() method return different object instances. Moreover, this concern is not pure theoretical. E.g. Iterable implementation used to pass values to a reduce method of Hadoop Reducer always returns the same value instance, just with different field values. So if you apply makeCollection from above (or CollectionUtils.addAll(Iterator)) you will end up with a collection with all identical elements.

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.