Arrays.asList() 创建的 List 上的 remove() 抛出 UnsupportedOperationException

问题描述

我有一个集合 c1 和一个数组 a.我正在尝试将数组转换为集合 c2 并执行 c1.removeAll(c2)，但这会引发 UnsupportedOperationException.我发现 Arrays 类的 asList() 返回 Arrays.ArrayList 类，这个类从 AbstractList 继承了 removeAll()() 其实现抛出 UnsupportedOperationException.

I have a collection c1<MyClass> and an array a<MyClass>. I am trying to convert the array to a collection c2 and do c1.removeAll(c2), But this throws UnsupportedOperationException. I found that the asList() of Arrays class returns Arrays.ArrayList class and the this class inherits the removeAll() from AbstractList() whose implementation throws UnsupportedOperationException.

    Myclass la[] = getMyClass();
    Collection c = Arrays.asList(la);
    c.removeAll(thisAllreadyExistingMyClass);

有什么办法可以去除元素吗?请帮忙

Is there any way to remove the elements? please help

推荐答案

Arrays.asList 返回一个围绕数组的 List 包装器.这个包装器有一个固定的大小并直接由数组支持，因此对 set 的调用将修改数组，任何其他修改列表的方法都会抛出一个 UnsupportedOperationException.

Arrays.asList returns a List wrapper around an array. This wrapper has a fixed size and is directly backed by the array, and as such calls to set will modify the array, and any other method that modifies the list will throw an UnsupportedOperationException.

要解决此问题，您必须通过复制包装器列表的内容来创建一个新的可修改列表.使用带有 Collection 的 ArrayList 构造函数很容易做到这一点:

To fix this, you have to create a new modifiable list by copying the wrapper list's contents. This is easy to do by using the ArrayList constructor that takes a Collection:

Collection c = new ArrayList(Arrays.asList(la));

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