CODEWITHSUNDEEP
java-8java-stream
rohit
rohit

Reputation: 96

Java stream operations

I have an object, "Item" with fields: int: id String: prices

The string prices contains one or more price values separated by comma.

Problem: Using stream operations I want a map of type Map<Integer,Set<Integer>> from List<Item> items

where key of Map is id and Set has value of prices as Integer extracted from the String prices.

There will be repeated ids in the List and can have different price strings.

I have come up with an approach which produces the following result:

Map<Integer, Set<List<Integer>>> itemStoresMapIntermediate = items.stream()
            .collect(Collectors.groupingBy(Item::getItemId,Collectors.mapping(Item::getStoresAsIntList, Collectors.toSet())));

getStoresAsIntList() returns List of price values from String prices in the object.

The above is certainly not what I want.

Upvotes: 2

Views: 95

Answers (1)

Eugene
Eugene

Reputation: 121048

If I understood correctly...

 Item item1 = new Item(1, "22,23,24");
 Item item2 = new Item(2, "33,34,35");
 Item item3 = new Item(1, "22,57,58");

 Map<Integer, Set<Integer>> map = Stream.of(item1, item2, item3)
            .collect(Collectors.toMap(
                    Item::getId,
                    i -> new HashSet<>(i.getStoresAsIntList()),
                    (left, right) -> {
                        left.addAll(right);
                        return left;
                    }, HashMap::new));

 System.out.println(map); // {1=[22, 23, 24, 57, 58], 2=[33, 34, 35]}

Upvotes: 5

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