如何将包含整数的 ArrayList 转换为原始 int 数组? [英] How to convert an ArrayList containing Integers to primitive int array?
问题描述
我正在尝试使用以下代码将包含 Integer 对象的 ArrayList 转换为原始 int[],但它引发了编译时错误.是否可以在 Java 中进行转换?
I'm trying to convert an ArrayList containing Integer objects to primitive int[] with the following piece of code, but it is throwing compile time error. Is it possible to convert in Java?
List<Integer> x = new ArrayList<Integer>();
int[] n = (int[])x.toArray(int[x.size()]);
推荐答案
您可以转换,但我认为没有任何内置功能可以自动执行此操作:
You can convert, but I don't think there's anything built in to do it automatically:
public static int[] convertIntegers(List<Integer> integers)
{
int[] ret = new int[integers.size()];
for (int i=0; i < ret.length; i++)
{
ret[i] = integers.get(i).intValue();
}
return ret;
}
(请注意,如果 integers
或其中的任何元素为 null
,这将抛出 NullPointerException.)
(Note that this will throw a NullPointerException if either integers
or any element within it is null
.)
根据评论,您可能希望使用列表迭代器来避免诸如 LinkedList
之类的列表的讨厌成本:
As per comments, you may want to use the list iterator to avoid nasty costs with lists such as LinkedList
:
public static int[] convertIntegers(List<Integer> integers)
{
int[] ret = new int[integers.size()];
Iterator<Integer> iterator = integers.iterator();
for (int i = 0; i < ret.length; i++)
{
ret[i] = iterator.next().intValue();
}
return ret;
}
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