CODEWITHSUNDEEP
javajava-8java-streamoption-type
user09
user09

Reputation: 956

Stream in orElse of optional

I am trying to use a Stream in orElse and having difficulty in understanding the error.

collectorConfiguration = Optional.ofNullable(recapPlacement.getAttId())
    .map(attId -> Optional.ofNullable(processorEngine.buildFrimFromAttId(attId))
         .orElseThrow( () -> new OmegaException("UnableToFirmByAttId", recapPlacement.getAttId())))
    .orElse( () -> Optional.ofNullable(collectorConfigurations.stream() //getting error here
        .filter(cc -> recapPlacement.getPnetCode().equals(cc.getPnetCode()))
        .filter(Objects::nonNull)
        .findFirst())
        .orElseThrow( () -> new OmegaException("CollectorCouldNotMapForPnetCode", recapPlacement.getPnetCode()))
    );

Overall in the above code I am trying to

  1. get collectorConfig if attId is not null

  2. if attId is not null and collectorConfig not found for that attId then I am throwing exception

  3. if attId is null then I am using pnet code to get collectConfig by streaming collectConfigurations list

  4. if collectConfig is not found for pnetCode then I am throwing exception

It is giving a compilation error 'Target type of a lambda expression must be an interface' in the orElse block.

Upvotes: 3

Views: 1228

Answers (2)

Naman
Naman

Reputation: 31878

You might want to replace 

.orElse( () -> Optional.ofNullable(collectorConfigurations.stream() //getting error here

with Optional.orElseGet which expects a Supplier as :

.orElseGet( () -> Optional.ofNullable(collectorConfigurations.stream() ...

In addition to the above, you shouldn't need the Optional.ofNullable in the supplier 

.orElseGet( () -> collectorConfigurations.stream()
    .filter(cc -> recapPlacement.getPnetCode().equals(cc.getPnetCode()))
    .filter(Objects::nonNull) //non-null filtered
    .findFirst()) // optional
    .orElseThrow( () -> new OmegaException("CollectorCouldNotMapForPnet...

Upvotes: 4

OhleC
OhleC

Reputation: 2890

orElse takes a regular value, not anything that could be represented by a lambda. Simply removing the () -> should help. Alternatively, you might have meant to call orElseGet

Upvotes: 1

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