public static int amountKurse (List<Studie> lstd) {
int result = (int) lstd.stream().map(Studie::getKurse).count();
return result;
}
private Map<Kurs,Integer> kurse = new HashMap<>();
public Set<Kurs> getKurse(){
return kurse.keySet();
}
I want to count the number of Kurse in all my Studie objects.
My current result is 20, when it should be 132
I am guessing that my function is only counting the amount of Studie
Would be grateful for some help on this.
If getKurse() returns a Set and you want to count the total number of elements of all these Sets, use:
int result = (int) lstd.stream().flatMap(s -> s.getKurse().stream()).count();
or, if you want to avoid counting duplicates:
int result = (int) lstd.stream().flatMap(s -> s.getKurse().stream()).distinct().count();
Use flatMap in order to flatten your stream of Studie to stream of Kurse. Then simply .count() the items in the stream:
int count = (int) lstd.stream() // Stream<Studie>
.map(Studie::getKurse) // Stream<Set<Kurse>>
.flatMap(Set::stream) // Stream<Kurse>
.count();