CODEWITHSUNDEEP
javaarrayscollections
Ezequiel
Ezequiel

Reputation: 3592

Null array to empty list

Arrays.asList(E[] e) returns a view of the array as a List, but when array is null it throws a NullPointerException.

Arrays.asList(null); //NullPointerException.

Actually I'm doing

 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).

How would you solve this problem?

Upvotes: 34

Views: 49274

Answers (3)

Nicolas Henneaux
Nicolas Henneaux

Reputation: 12215

You can use Java 8 Optionaland Stream

Optional.ofNullable(possibleNullArray)
        .map(Arrays::stream)
        .orElseGet(Stream::empty)
        .collect(Collectors.toList())

Upvotes: 21

Petr Janeček
Petr Janeček

Reputation: 38424

I'm not aware of any util method in Apache Commons / Guava that would create an empty List instance out of null.

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.

SomeObject[] array = ArrayUtils.nullToEmpty(possiblyNullArray);

Upvotes: 21

Eran
Eran

Reputation: 393831

You can use Java 8 Optional:

String[] arr = null;
List<String> list = Arrays.asList(Optional.ofNullable(arr).orElse(new String[0]));

Upvotes: 46

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