http://stackoverflow.com/questions/31947433/rxjava-sequence-filtering#31947555

StackOverflow.java

public class StackOverflow {
  public static void main(String[] args) {
    final Observable<Integer> firstObs = Observable.just(1, 2, 3, 4, 5);
    final Observable<Integer> secondObs = Observable.just(2, 4, 6);

    final Observable<Integer> result = secondObs.toList().flatMap(new Func1<List<Integer>, Observable<Integer>>() {
      @Override
      public Observable<Integer> call(final List<Integer> ignore) {
        return firstObs.filter(new Func1<Integer, Boolean>() {
          @Override
          public Boolean call(final Integer value) {
            return !ignore.contains(value);
          }
        });
      }
    });

    result.subscribe(new Action1<Integer>() {
      @Override
      public void call(Integer integer) {
        System.out.println("" + integer);
      }
    });
  }
}