RxJava: buffer items until some condition is true for current item

Question

Here\'s a snippet I\'m trying to figure out:

class RaceCondition {

    Subject subject = Pu         


        

Answer 1

If I understand correctly, you want to buffer until some predicate allows it based on the items. You can do this with a complicated set of operators but perhaps its easier to just write a custom operator:

public final class BufferUntil<T> 
implements Operator<List<T>, T>{

    final Func1<T, Boolean> boundaryPredicate;

    public BufferUntil(Func1<T, Boolean> boundaryPredicate) {
        this.boundaryPredicate = boundaryPredicate;
    }

    @Override
    public Subscriber<? super T> call(
            Subscriber<? super List<T>> child) {
        BufferWhileSubscriber parent = 
                new BufferWhileSubscriber(child);
        child.add(parent);
        return parent;
    }

    final class BufferWhileSubscriber extends Subscriber<T> {
        final Subscriber<? super List<T>> actual;

        List<T> buffer = new ArrayList<>();

        /**
         * @param actual
         */
        public BufferWhileSubscriber(
                Subscriber<? super List<T>> actual) {
            this.actual = actual;
        }

        @Override
        public void onNext(T t) {
            buffer.add(t);
            if (boundaryPredicate.call(t)) {
                actual.onNext(buffer);
                buffer = new ArrayList<>();
            }
        }

        @Override
        public void onError(Throwable e) {
            buffer = null;
            actual.onError(e);
        }

        @Override
        public void onCompleted() {
            List<T> b = buffer;
            buffer = null;
            if (!b.isEmpty()) {
                actual.onNext(b);
            }
            actual.onCompleted();
        }
    }
}