removeIf() of List not working throwing - UnsupportedOperationException

Question

When I try to remove the element from the list using removeIf(), It is throwing UnsupportedOperationException

public class T {
        public static void main(String[] args) {
        String[] arr = new String[] { "1", "2", "3" };
        List<String> stringList = Arrays.asList(arr);
        stringList.removeIf((String string) -> string.equals("2"));
    }
}

Can some one help me understand why this is happening and how can I rectify this ?

`Arrays.asList()` returns an unmodifiable list. You can't change its content — ernest_k, May 10 '18 at 05:57
As an aside, you don't need the type or parentheses in the lambda: these can be inferred. — Andy Turner, May 10 '18 at 06:15
@Ernest you can change the list, but only using `set` (or `replaceAll`). It is fixed-size, not unmodifiable. — Andy Turner, May 10 '18 at 06:17

score 10 · Answer 1 · answered May 10 '18 at 05:57

10

Arrays.asList(arr) returns a fixed sized List, so you can't add or remove elements from it (only replace existing elements).

Create an ArrayList instead:

List<String> stringList = new ArrayList<>(Arrays.asList(arr));

answered May 10 '18 at 05:57

Eran

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score 1 · Answer 2 · answered May 10 '18 at 06:12

1

Since you are explicitly calling Arrays.asList, consider the alternative of not doing that, and create the filtered list directly:

Stream.of(arr)
    .filter(string -> !string.equals("2"))
    .collect(Collectors.toList())

answered May 10 '18 at 06:12

Andy Turner

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removeIf() of List not working throwing - UnsupportedOperationException

2 Answers2