何时应该接受可迭代的参数< T>与集合< T>在Java？ [英] When should I accept a parameter of Iterable<T> vs. Collection<T> in Java?

问题描述

在Java中使用 Iterable< T> 与集合< T> 例如，考虑实现一个主要涉及包含 Foo 的集合的类型，以及一些关联的元数据。这种类型的构造函数允许对象列表的一次性初始化。 （元数据可以稍后设置。）这个构造函数接受什么类型？ Iterable 或 Collection ？

遵循 ArrayList 它可以从任何 Collection 初始化，但不 Iterable

但是为什么不接受 Iterable< Foo> code>，因为这足以满足初始化需求？为什么要求消费者提供比严格必要的功能（ Collection ）更高的级别（ Iterable ）？ / p>


解决方案

许多集合类型在 Iterable< T> 仅仅在1.5中引入） - 没有理由添加构造函数以接受 Iterable< T> 以及 集合< T> 但是改变现有构造函数将是一个突变。





我将使用 Iterable< T> 如果这允许你做你想要的一切。它对于调用者更灵活，特别是它允许您使用Google Java Collections（毫无疑问类似的库）相对轻松过滤/投影等。

What are the considerations of using Iterable<T> vs. Collection<T> in Java?

For example, consider implementing a type that is primarily concerned with containing a collection of Foos, and some associated metadata. The constructor of this type allows one-time initialisation of the object list. (The metadata can be set later.) What type should this constructor accept? Iterable<Foo>, or Collection<Foo>?

What are the considerations for this decision?

Following the pattern set forth by library types such as ArrayList (which can be initialised from any Collection, but not an Iterable) would lead me to use Collection<Foo>.

But why not accept Iterable<Foo>, given that this is is sufficient for the initialisation needs? Why demand a higher level of functionality (Collection) from the consumer, than what is strictly necessary (Iterable)?

解决方案

Many of the collection types existed before Iterable<T> (which was only introduced in 1.5) - there was little reason to add a constructor to accept Iterable<T> as well as Collection<T> but changing the existing constructor would have been a breaking change.

Personally I would use Iterable<T> if that allows you to do everything you want it to. It's more flexible for callers, and in particular it lets you do relatively easy filtering/projection/etc using the Google Java Collections (and no doubt similar libraries).

这篇关于何时应该接受可迭代的参数< T>与集合< T>在Java？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！