Lambda Expression object mapping issue

Question

I have PrimaryDTO class which contains a List<SecondaryDTO> and this SecondaryDTO itself contains a Set<SecondaryCategoryDTO> and finally this SecondaryCategoryDTO contains a boolean status.

In the below statement, I want to check if any status is true then go inside if statement else don't enter.

if(Optional.ofNullable(PrimaryDTO.getSecondaryDTOs()).
    orElse(PrimaryDTO.getSecondaryDTOs()).stream().filter(Objects::nonNull)
    .map(x->x.getSecondaryCategories()).anyMatch(z-> z.isStatus()==true))

But, in the above syntax, z.isStatus() is giving error as it is saying z to be a set. I am already iterating Set via .map with getSecondaryCategories(). I am not getting why it is taking it as set?

What’s the purpose of Optional.ofNullable(PrimaryDTO.getSecondaryDTOs()). orElse(PrimaryDTO.getSecondaryDTOs())? Doesn’t it always evaluate to PrimaryDTO.getSecondaryDTOs(), no matter whether it is null? Besides that, you are not iterating the Set, you are just mapping to it. Perhaps, you meant .flatMap(x -> x.getSecondaryCategories().stream())… — Holger
– Holger, Commented Oct 19, 2018 at 14:56
Thanks @Holger for the comment on Optional, Its a mistake. I didn't got on how to execute the statement if not null since if I use ifPresent, then I cannot throw any Exception from inside it. It asks for try catch block. — Bogl
– Bogl, Commented Oct 19, 2018 at 15:13

Eugene · Accepted Answer · 2018-10-19 15:18:37Z

1

It seems like you might have PrimaryDTO as a null and it's List<SecondaryDTO> as a null, and some elements in that List might be null also, in such a case:

Optional<Boolean> op = Optional.ofNullable(primaryDTO)
            .flatMap(x -> Optional.ofNullable(x.getSecondaryDTOs()))
            .map(x -> x.stream()
                    .filter(Objects::nonNull)
                    .flatMap(y -> y.getSecondaryCategoryDTOs().stream())
                    .map(SecondaryCategoryDTO::isStatus)
                    .anyMatch(z -> z == true)); 

if(op.isPresent()){
    // do your work
}

answered Oct 19, 2018 at 15:18

Eugene

122k17 gold badges219 silver badges335 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Bogl Over a year ago

Thanks Eugene and Holger for the solution. Its working now. I tried with flatmap but in an incorrect way.

Ousmane D. Over a year ago

@harshit if you want everything inside the if condition

if(Optional.ofNullable(primaryDTO)                 .flatMap(x -> Optional.ofNullable(x.getSecondaryDTOs()))                 .filter(x -> x.stream()                         .filter(Objects::nonNull)                         .flatMap(y -> y.getSecondaryCategories().stream())                         .anyMatch(SecondaryCategoryDTO::isStatus)).isPresent()){...};

Ousmane D. Over a year ago

.map(SecondaryCategoryDTO::isStatus) .anyMatch(z -> z == true) could be simplified to .anyMatch(SecondaryCategoryDTO::isStatus)

Eugene Over a year ago

@Aomine this is how I wanted to do initially, but since the OP seems to be confused about Optional in general, i wanted to be as verbose as I could here...

Bogl Over a year ago

Thanks @Aomine for the alternative solution. It is much helpful. Eugene, Thanks for the simplified solution as it was easy to understand the thing.

|

Collectives™ on Stack Overflow

Lambda Expression object mapping issue

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related