Operator - GroupBy

GroupBy

divide an Observable into a set of Observables that each emit a different subset of items from the original Observable

The GroupBy operator divides an Observable that emits items into an Observable that emits Observables, each one of which emits some subset of the items from the original source Observable. Which items end up on which Observable is typically decided by a discriminating function that evaluates each item and assigns it a key. All items with the same key are emitted by the same Observable.

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        Observable
                .just(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
                .doOnNext(item -> System.out.println("source emitting " + item))
                .groupBy(item -> {
                    System.out.println("groupBy called for " + item);
                    return item % 3;
                })
                .subscribe(observable -> {
                    System.out.println("got observable " + observable + " for key " + observable.getKey());
                    observable.subscribe(item -> {
                        System.out.println("key " + observable.getKey() + ", item " + item);
                    });

                });

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