问题描述
与 Collections.singletonList(something) 相比，使用 Arrays.asList(something) 制作包含一个项目的列表是否有优势(或有很大不同)?后者也使返回的列表不可变.
Is there an advantage (or much of a difference) to using Arrays.asList(something) over Collections.singletonList(something) to make a list containing one item? The latter makes the returned list immutable as well.
推荐答案
Collections.singletonList(something) 是 immutable 而 Arrays.asList(something) 是一个固定大小的 List 表示，其中 List 和 Array 在堆中连接.
Collections.singletonList(something) is immutable whereas Arrays.asList(something) is a fixed size List representation of an Array where the List and Array gets joined in the heap.
Arrays.asList(something) 允许对其进行非结构性更改，这会反映到 List 和联合数组中.它会抛出 UnsupportedOperationException 以添加、删除元素，尽管您可以为特定索引设置元素.
Arrays.asList(something) allows non-structural changes made to it, which gets reflected to both the List and the conjoined array. It throws UnsupportedOperationException for adding, removing elements although you can set an element for a particular index.
对Collections.singletonList(something) 返回的列表所做的任何更改都将导致UnsupportedOperationException.
Any changes made to the List returned by Collections.singletonList(something) will result in UnsupportedOperationException.
此外，Collections.singletonList(something) 返回的 List 的容量将始终为 1 与 Arrays.asList(something) 不同其容量将是支持数组的大小.
Also, the capacity of the List returned by Collections.singletonList(something) will always be 1 unlike Arrays.asList(something) whose capacity will be the size of the backed array.
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