// "Collapse loop with stream 'sum()'" "true-preview"

import java.util.List;
import java.util.Objects;

public class Main {
  interface Person {
    int getAge();
  }

  public long test(List<Person> collection) {
    long i = collection.stream().filter(Objects::nonNull).mapToLong(Person::getAge).sum();
      return i;
  }
}