Java 9中的Convenience Factory Method返回的特定集合类型 [英] Specific Collection type returned by Convenience Factory Method in Java 9

问题描述

在Java 9中，我们有方便工厂方法来创建和实例化不可变的List，Set和Map。

In Java 9 we have convenience factory methods to create and instantiate immutable List, Set and Map.

但是，目前还不清楚返回对象的具体类型。

However, it is unclear about the specific type of the returned object.

例如：

List list = List.of("item1", "item2", "item3");

在这种情况下，实际返回了哪种类型的列表？它是一个ArrayList或LinkedList还是其他类型的List？

In this case which type of list is actually returned? Is it an ArrayList or a LinkedList or some other type of List?

API文档刚提到这一行，没有明确提到它的LinkedList：

The API documentation just mentions this line, without explicitly mentioning that its a LinkedList:

列表中元素的顺序与
提供的参数或提供的数组中的元素的顺序相同。

The order of elements in the list is the same as the order of the provided arguments, or of the elements in the provided array.

推荐答案

List.of 是包私有静态类之一，因此不属于公共API：

The class returned by List.of is one of the package-private static classes and therefore not part of the public API:

package java.util;
...

class ImmutableCollections {
    ...

    static final class List0<E> extends AbstractImmutableList<E> {
        ...
    }

    static final class List1<E> extends AbstractImmutableList<E> {
        ...
    }

    static final class List2<E> extends AbstractImmutableList<E> {
        ...
    }

    static final class ListN<E> extends AbstractImmutableList<E> {
        ...
    }
}

所以这是不是ArrayList（既不是LinkedList）。您需要知道的唯一事情是不可变并且满足 List 接口合约。

So this is not an ArrayList (neither a LinkedList). The only things you need to know is that it is immutable and satisfies the List interface contract.

这篇关于Java 9中的Convenience Factory Method返回的特定集合类型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！