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javaguavalambdaj

Find intersection between collections with different objects

I have list of custom objects like below:

List<CustomObject> existingValues

And another collection with ids that has been sent from client and contains ids of CustomObject mentoioned above Set<Long> ids.

My goal is to return collection with CustomObject that will contains only elements where ids intersect.

I can simply do this with nested for each cycles. But it looks a bit ugly.

In SQL I can do similar stuff with query:

select * where customobject.id in (some ids...)

In wich way it can be achived with lamdaj or guava?

Solution

  • With Guava this is done as follows:

        final Set<Long> ids = ...; //initialize correctly

    List<CustomObject> results = FluentIterable.from(existingValues).filter(new Predicate<CustomObject>() {
        @Override
        public boolean apply(final CustomObject input) {
            return ids.contains(input.getId());
        }
    }).toList();