使用 Arrays.asList() 创建列表的好处 [英] Benefits of creating a List using Arrays.asList()

问题描述

参考Arrays.asList(array) vs new ArrayList的区别<Integer>(Arrays.asList(ia)) in java我很好奇 Arrays.asList() 方法的确切目的是什么.

Referring to Difference between Arrays.asList(array) vs new ArrayList<Integer>(Arrays.asList(ia)) in java I was curious as in what's the exact purpose of Arrays.asList() method.

当我们从它创建一个新的 List 时，比如说 -

When we create a new List from it, say for example -

Integer[] I = new Integer[] { new Integer(1), new Integer(2), new Integer(3) };
List<Integer> list1 = Arrays.asList(I);
List<Integer> list2 = ((List<Integer>) Arrays.asList(I));

我们无法对其执行大多数常规操作，例如 .add()、.remove().因此，我无法向其添加迭代器以避免并发修改.

We cannot perform most of the the regular operations on it like .add(), .remove(). Thus, I was not able add an iterator to it to avoid concurrent modification.

Oracle 文档状态

Oracle docs state

public static List asList(T... a)

public static List asList(T... a)

返回由指定数组支持的固定大小列表.(更改为返回的列表直写"到数组中.)此方法充当结合基于数组和基于集合的 API 之间的桥梁使用 Collection.toArray().返回的列表是可序列化的，并且实现 RandomAccess.

Returns a fixed-size list backed by the specified array. (Changes to the returned list "write through" to the array.) This method acts as bridge between array-based and collection-based APIs, in combination with Collection.toArray(). The returned list is serializable and implements RandomAccess.

它适用于创建一个新的List.Listlist3 = new ArrayList<>(Arrays.asList(I));

It works well with creating a new List. List<Integer> list3 = new ArrayList<>(Arrays.asList(I));

那么，为什么会这样?它的优点和缺点是什么?

So, why this and what are its advantages and disadvantages?

推荐答案

不能调用 add、remove 等是完全不同的.如果您不需要这些方法，Arrays.asList 为您提供了一个完美的数组视图作为列表(对于采用集合而不是数组的 API).如果您需要更改列表的形状"，那么 new ArrayList<>(Arrays.asList(myArray)) 是您要走的路.

Not being able to call add, remove, etc is the exact difference. If you don't need those methods, Arrays.asList gives you a perfectly fine view of the array as a List (for APIs that take collections rather than arrays). If you need to change the "shape" of the list, then new ArrayList<>(Arrays.asList(myArray)) is the way to go.

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