Arrays.stream（array）vs Arrays.asList（array）.stream（） [英] Arrays.stream(array) vs Arrays.asList(array).stream()

问题描述

在这个问题中，已经回答过两个表达式都相等，但在这种情况下，它们会产生不同的结果。对于给定的 int []得分，为什么这样做：

In this question it has already been answered that both expressions are equal, but in this case they produce different results. For a given int[] scores, why does this work:

Arrays.stream(scores)
        .forEach(System.out::println);

...但这不是：

Arrays.asList(scores).stream()
        .forEach(System.out::println);

据我所知 .stream（）可以在任何Collection上调用，列表肯定是。第二个代码片段只返回一个包含整个数组而不是元素的流。

As far as I know .stream() can be called on any Collection, which Lists definitely are. The second code snippet just returns a stream containing the array as a whole instead of the elements.

推荐答案

你看到的行为不是特定于 Stream s。
Arrays.asList（得分）在传递给它时返回 List< int []> 一个 int [] ，因为泛型类型参数不能被基本类型替换。因此，当您调用 asList（T ... a）时，编译器使用 int [] 代替 T 。

The behavior you see is not specific to Streams. Arrays.asList(scores) returns a List<int[]> when you pass to it an int[], since a generic type parameter can't be replaced by a primitive type. Therefore, when you call asList(T... a), the compiler uses int[] in place of T.

如果您将得分更改为整数[] ，你会得到你期望的输出（即 Arrays.asList（得分）将返回列表<整数> ） 。

If you change scores to Integer[], you'll get the output you expect (i.e. Arrays.asList(scores) will return a List<Integer>).

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