How to find count of objects within a list

Question

I have an object:

Trip {
        private TripName tripName;
        private List<TripStops> tripStops;
}

Trip Stops contains

TripStops {
           private PackageObject packageObject;
           private PackageTask packageTask;
}

I'm trying to get the count of PackageObject inside trip stop using Java8.

Will I be able to do something like this? Or is there a better way

Integer packageCount = Trip.getTripStops.stream().filter(TripStops::getPackageObject).count

Ousmane D. · Accepted Answer · 2018-10-19 20:16:51Z

4

To interpret the sentence "I'm trying to get the count of PackageObject inside trip stop" into code would be:

long count = Trip.getTripStops().stream().count();

or simply:

int count = Trip.getTripStops().size();

as each TripStops has one instance of PackageObject.

However, to get a count of the elements returned from TripStops::getPackageObject which pass a given criteria:

long count = Trip.getTripStops().stream()
                                .map(TripStops::getPackageObject)
                                .filter(criteria) // where criteria is the condition to be passed
                                .count();

// or merge map/filter into one with ---> .filter(t -> t.getPackageObject()...)

edited Oct 19, 2018 at 20:16

answered Oct 19, 2018 at 20:11

Ousmane D.

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1 Comment

Ousmane D. Over a year ago

@Buccaneer you’re more than welcome. As a way of saying “thank you” you could upvote the answer and mark it as accepted. ;)

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