尝试从Array.asList返回的列表中删除UnsupportedOperationException [英] UnsupportedOperationException when trying to remove from the list returned by Array.asList

问题描述

我正在使用列表来保存通过调用 Array.asList（）方法获取的一些数据。然后我试图使用 myList.Remove（int i）方法删除一个元素。但是当我尝试这样做时，我得到一个 UnsupportedOperationException 。这是什么原因？如何解决这个问题？

I am using a List to hold some data obtained by calling Array.asList() method. Then I am trying to remove an element using myList.Remove(int i) method. But while I try to do that I am getting an UnsupportedOperationException. What would be the reason for this? How should I resolve this problem?

推荐答案

Array.asList（） 在列表界面中包含一个数组。该列表仍然由数组支持。数组是一个固定的大小 - 它们不支持添加或删除元素，因此包装器也不能。

Array.asList() wraps an array in the list interface. The list is still backed by the array. Arrays are a fixed size - they don't support adding or removing elements, so the wrapper can't either.

文档不会像这样清楚可能，但他们说：

The docs don't make this as clear as they might, but they do say:

返回由指定数组支持的固定大小的列表。 p>

Returns a fixed-size list backed by the specified array.

固定大小位应该是一个提示，您不能添加或删除元素：）

The "fixed-size" bit should be a hint that you can't add or remove elements :)

虽然还有其他方法（其他方法可以从数组创建一个新的 ArrayList ）而不需要额外的库，我个人建议保留 Google Collections Library （或，发布时）.google.com / p / guava-libraries /rel =noreferrer> Guava 。然后，您可以使用：

Although there are other ways around this (other ways to create a new ArrayList from an array) without extra libraries, I'd personally recommend getting hold of the Google Collections Library (or Guava, when it's released). You can then use:

List<Integer> list = Lists.newArrayList(array);

我建议这样做的原因是，GCL是一般的好东西，值得使用

The reason I'm suggesting this is that the GCL is a generally good thing, and well worth using.

如注释所述，这需要一个复制的数组;该列表不受原始数组的支持，而另一个集合中的更改将不会在另一个集合中显示。

As noted in comments, this takes a copy of the array; the list is not backed by the original array, and changes in either collection will not be seen in the other.

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