CODEWITHSUNDEEP
javacollectionsjava-stream
whiteErru
whiteErru

Reputation: 275

Remove some values from collection of collections using java streams

Imagine a collection of collections(set of sets):

    Set<Set<Long>> setOfSets = new HashSet<>();
    Set<Long> set = new HashSet<>();
    set.add(4L);
    set.add(3L);
    set.add(8L);
    setOfSets.add(set);
    set = new HashSet<>();
    set.add(6L);
    set.add(7L);
    set.add(4L);
    setOfSets.add(set);

How do I remove given value from this collection using java streams? For example if the given value is 4 then expected sets should be equal to {[3, 8][6, 7]}. I know that this is possible with iterating through the collection(s) using nested for loops, but I'm specifically interested in using streams.

Upvotes: 2

Views: 78

Answers (2)

Rogue
Rogue

Reputation: 11483

Since they're pass-by-reference, you can just mutate them directly:

int removeNum = 4;
setOfSets.forEach(s -> s.remove(removeNum));

//add it to each
setOfSets.forEach(s -> s.add(removeNum));

While it isn't technically a stream solution, it's pretty much along those lines.

Upvotes: 1

sergeyan
sergeyan

Reputation: 1183

Set<Set<Long>> result = setOfSets.stream()
                                 .map(s -> s.stream()
                                            .filter(id -> (id != 4L))
                                            .collect(Collectors.toSet()))
                                 .collect(Collectors.toSet());

Upvotes: 1

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