Java 空数组到空列表
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Null array to empty list
提问by Ezequiel
Arrays.asList(E[] e)returns a view of the array as a List, but when array is null it throws a NullPointerException.
Arrays.asList(E[] e)将数组的视图作为 a 返回List，但是当数组为 null 时，它会抛出 a NullPointerException。
Arrays.asList(null); //NullPointerException.
Actually I'm doing
其实我在做
List list = possibleNullArray != null ? Arrays.asList(possibleNullArray) : Collections.EMPTY_LIST;
However, creating a Utility class in my project only for this purpose is a thing that I prefer not to do. Is there some utility Class, or library like Apache Commons or Guava to convert null arrays to empty List? (i.e. a null-safe converter between arrays and Collections).
但是，仅出于此目的在我的项目中创建 Utility 类是我不愿意做的事情。是否有一些实用程序类或像 Apache Commons 或 Guava 这样的库可以将空数组转换为空数组List？（即数组和集合之间的空安全转换器）。
How would you solve this problem?
你会如何解决这个问题？
采纳答案by Petr Jane?ek
I'm not aware of any util method in Apache Commons / Guava that would create an empty Listinstance out of null.
我不知道 Apache Commons / Guava 中的任何 util 方法会List从 null创建一个空实例。
The best thing you can probably do is to initialize the possibly null array beforehand, e.g. with ArrayUtils.nullToEmpty(). Get rid of the null as soon as you can.
您可能做的最好的事情是事先初始化可能为空的数组，例如使用ArrayUtils.nullToEmpty(). 尽快摆脱空值。
SomeObject[] array = ArrayUtils.nullToEmpty(possiblyNullArray);
回答by Eran
You can use Java 8 Optional:
您可以使用 Java 8 Optional：
String[] arr = null;
List<String> list = Arrays.asList(Optional.ofNullable(arr).orElse(new String[0]));
回答by Nicolas Henneaux
You can use Java 8 Optionaland Stream
您可以使用 Java 8Optional和Stream
Optional.ofNullable(possibleNullArray)
.map(Arrays::stream)
.orElseGet(Stream::empty)
.collect(Collectors.toList())
