使用Java的Collections.singletonList（）？ [英] Use of Java's Collections.singletonList()?

问题描述

Java中使用 Collections.singletonList（）有什么用？我知道它返回一个包含一个元素的列表。为什么我想要一个单独的方法来做到这一点？不变性如何在这里发挥作用？

What is the use of Collections.singletonList() in Java? I understand that it returns a list with one element. Why would I want to have a separate method to do that? How does immutability play a role here?

此方法是否有任何特殊的有用用例，而不仅仅是一种方便的方法？

Are there any special useful use-cases for this method rather than just being a convenient method?

推荐答案

javadoc 说：

返回包含不可变列表只有指定的对象。返回的列表是可序列化的。

你问：

为什么我想要一个单独的方法呢？

Why would I want to have a separate method to do that?

为方便起见...为了节省您必须编写一系列语句：

As a convenience ... to save you having to write a sequence of statements to:

• 创建一个空列表对象


• 添加一个元素，


• 用不可变包装器包装它。

不变性在这里如何发挥作用？

How does immutability play a role here?

这是方法规范的一部分;见上文。

It is part of the specification of the method; see above.

此方法是否有任何特殊有用的用例，而不仅仅是一种方便的方法？

Are there any special useful use-cases for this method, rather than just being a convenience method?

显然，有些用例可以方便地使用 singletonList 方法。但我不知道你会如何（客观地）区分普通用例和特别有用用例...

Clearly, there are use-cases where it is convenient to use the singletonList method. But I don't know how you would (objectively) distinguish between an ordinary use-case and a "specially useful" one ...

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