Logging the result of filter while using java streams filter by predicate

Question

The scenario is there are different types of filters I have created which filters the list of some objects based on the property of the object.

So for that I have

Answer 1

perhaps not the prettiest solution, but it works and you only change your abstract base class:

abstract class AbstractEventFilter {

    private final Logger logger = Logger.getLogger(getClass().getCanonicalName());
    private final String filterName = getClass().getSimpleName();

    protected abstract Predicate isEligible();

    private Predicate internalIsEligible() {
        return iEvent -> {
            boolean res = isEligible().test(iEvent);
            if (!res) {
                logger.info("event " + iEvent.toString() + " filtered by " + filterName);
            }
            return res;
        };
    }

    public List getFilteredEvents(final List events) {
        return events.stream().filter(internalIsEligible()).collect(Collectors.toList());
    }
}

you keep your derived classes implementing isELigible() as before, only in your getFilteredEvents method, you call the internalIsEligibable method instead.