Create new Object to replace values in an immutable Object

debugcn Published at Dev

karvai

I have immutable objects as follows.

@Getter 
@Builder 
class MainDetail {
    // 5 other String fields
    private Data data;
}

@Getter 
@Builder 
class ImageUrl {
    private final String dataOne; // looking to change these 2 values
    private final String dataTwo; // if rest call returns null for these. 
}

Information to fill these up is fetched from a rest call, working fine as follows.

List<MainDetail> featureBenefits = // value from a rest response

I wish to switch out the dataOne and dataTwo values in here if it is null for each MainDetail Object.
I can't just use a set method to do this cos it is immutable.

I end up with the following verbose way of doing it where I need to do multiple variations of the check to swap values.
I can't just check one at a time and switch cos Object becomes immutable. Can't add another if the second one is null too after that.

Is there a way to do this more elegantly, possibly via streams? Appreciate any help. Thanks.

List<MainDetail> mainDetails = new ArrayList<>();
for (MainDetail mainDetail : featureBenefits) {
    if (mainDetail.getImageUrl().getDataOne() == null && mainDetail.getImageUrl().getdataTwo() == null) {
        ImageUrl imageUrl = ImageUrl.builder()
                .dataOne("default1")
                .dataTwo("default12")
                .build();
        MainDetail detail = MainDetail.builder()
                .imageUrl(imageUrl)
                .build();
        mainDetails.add(detail);
    }
    else if (mainDetail.getImageUrl().getdataOne() == null) {
        ImageUrl imageUrl = ImageUrl.builder()
                .dataOne("default1")
                .build();
        MainDetail detail = MainDetail.builder()
                .imageUrl(imageUrl)
                .build();
        mainDetails.add(detail);
    }
    else if (mainDetail.getImageUrl().getDataTwo() == null) {
        ImageUrl imageUrl = ImageUrl.builder()
                .dataTwo("default2")
                .build();
        MainDetail detail = MainDetail.builder()
                .imageUrl(imageUrl)
                .build();
        mainDetails.add(detail);
    }
}

oleg.cherednik

What about this one:

List<MainDetail> featureBenefits = Collections.emptyList();
List<MainDetail> mainDetails = new ArrayList<>();

for (MainDetail mainDetail : featureBenefits) {
    ImageUrl imageUrl = mainDetail.getImageUrl();

    mainDetails.add(MainDetail.builder()
                              .imageUrl(ImageUrl.builder()
                                                .dataOne(Optional.ofNullable(imageUrl.getDataOne()).orElse("default1"))
                                                .dataTwo(Optional.ofNullable(imageUrl.getDataTwo()).orElse("default2"))
                                                .build())
                              .build());
}

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