CODEWITHSUNDEEP
javajava-stream
MadMax
MadMax

Reputation: 101

How to do multiple map operations with the same value using Java stream?

I have a "root" list which contains objects with different lists inside. I have it now divided in 3 operations but i think it could be done using only one so i wouldn't repeat code. Is it possible?

List<Prices[]> pricesList = new ArrayList<Prices>();
List<Instructions[]> instructionsList = new ArrayList<Instructions>();
List<Sizes[]> sizesList = new ArrayList<Sizes>();

/* storesList contains a list of Stores which each of them has 
   inside a list of prices, instructions and sizes. 
   I want join all of that individual lists into a single one.*/
 storesList.stream()
                .map(Devices::getDevicesSubtype)
                .filter(Objects::nonNull)
                .map(subtype -> (MobileSubtype) subtype)
                .map(MobileSubtype::getPrices)
                .forEachOrdered(list -> pricesList.add(list));

storesList.stream()
                .map(Devices::getDevicesSubtype)
                .filter(Objects::nonNull)
                .map(subtype -> (MobileSubtype) subtype)
                .map(MobileSubtype::getInstructions)
                .forEachOrdered(list -> instructionsList.add(list));

storesList.stream()
                .map(Devices::getDevicesSubtype)
                .filter(Objects::nonNull)
                .map(subtype -> (MobileSubtype) subtype)
                .map(MobileSubtype::getSizes)
                .forEachOrdered(list -> sizesList.add(list));

/*How could i not repeat this part of the code and do the 3 for each ordered?*/
storesList.stream()
                .map(Devices::getDevicesSubtype)
                .filter(Objects::nonNull)
                .map(subtype -> (MobileSubtype) subtype)

Upvotes: 0

Views: 223

Answers (1)

azro
azro

Reputation: 54148

Regarding your actual code, I'd suggest one forEach before mapping to a specific category, then add in each list

storesList.stream()
        .map(Devices::getDevicesSubtype)
        .filter(Objects::nonNull)
        .map(subtype -> (MobileSubtype) subtype)
        .forEachOrdered(subtype -> {
            pricesList.add(subtype.getPrices());
            instructionsList.add(subtype.getInstructions());
            sizesList.add(subtype.getSizes());
        });

Note : classes should be name at singular if there represent only one element, is Prices is one price, it should be name Price to avoid confusion, same for Instructions and Sizes

Upvotes: 2

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