Java 8 stream condition for null values

Question

I am using Java 8 stream

executeRequest(requestId).stream()
        .map(d-> (Response) d).collect(Collectors.toList());

the Response object is like this

@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
public class Response {

  String title;
  String id;
}

when the responses are null, I am getting an error because it is trying to collect null values in a list, I want to have a condition that when title is null, stream does not continue, or any thing that helps me to handle it

not quite sure on ur specification, should the thing be skipped or the whole stream be aborted? for former, use .filter(r -> r.title != null). for latter u might want to use .takeWhile(r -> r.title != null) or similar. — Zabuzard
– Zabuzard, Commented Nov 14, 2022 at 9:00
@Zabuzard as the r value is an object at first and in map I am converting it to Response, it hasn't a title option to check if it is null or not in the filter — Tindona
– Tindona, Commented Nov 14, 2022 at 9:05
thats also the wrong syntax for a lambda. u have to write .filter(r -> r.title != null). carefully read the suggestions. — Zabuzard
– Zabuzard, Commented Nov 14, 2022 at 9:53

Youcef LAIDANI · Accepted Answer · 2022-11-14 09:14:41Z

3

I think you need some think like this:

List<Response> response = executeRequest(requestId).stream()
    .filter(Objects::nonNull)                    // filter the object if not null
    .map(Response.class::cast)                   // cast the object
    .filter(r -> Objects.nonNull(r.getTitle()))  // filter by title if not null
    .collect(Collectors.toList());

answered Nov 14, 2022 at 9:14

Youcef LAIDANI

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Tsvetoslav Tsvetkov · Accepted Answer · 2022-11-14 09:30:40Z

3

I would suggest using.filter()

Try out this

executeRequest(requestId).stream()
.filter(Objects::nonNull)
.map(d-> (Response) d)
.filter(resp -> Objects.nonNull(resp.getTitle()))
.collect(Collectors.toList());

edited Nov 14, 2022 at 9:30

answered Nov 14, 2022 at 9:00

Tsvetoslav Tsvetkov

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3 Comments

Zabuzard Over a year ago

note that this only ensures that the Response object itself is not null. OP asked for the title (a field of Response) not being null.

Tindona Over a year ago

it doesn't work. executeRequest is returning a list of objects, the response is not null itself but the parameters inside it may be null, and I want to filter them

Tsvetoslav Tsvetkov Over a year ago

@Tindona Updated lambda

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