Stream api filter

Насколько я понимаю, вам нужно что-то такое

Set<Integer> stops = Stream.concat(
    passengers.stream().filter(x -> !x.isEntered()).map(Passenger::getDeparture),
    passengers.stream().map(Passenger::getDestination)
).collect(Collectors.toSet());
Stream<Integer> result = stations.stream().filter(stops::contains);

Думаю что-нибудь такое. Накидал так как представил по вашему разъяснению задачу.

class App {
  public static void main(String[] args) {
    List<Integer> stations = Arrays.asList(1, 2, 3, 4, 5);
    App outer = new App();
    List<Passenger> passengers = new ArrayList<>();
    passengers.add(outer.new Passenger(1));
    passengers.add(outer.new Passenger(2));
    passengers.add(outer.new Passenger(3));
    passengers.add(outer.new Passenger(4));
    System.out.println(passengers);
    List<Integer> newStations =
        stations.stream()
            .filter(
                station ->
                    passengers.stream().anyMatch(p -> !p.isEntered() && p.departure == station))
            .collect(Collectors.toList());
    System.out.println(newStations);
  }
  public class Passenger {
    private Integer number;
    private Integer departure;
    private Integer destination;
    private Boolean entered;
    public Passenger(Integer number) {
      this.departure = (int) (Math.random() * 5) + 1;
      this.destination = (int) (Math.random() * 5) + 1;
      this.entered = false;
      this.number = number;
    }
    public Integer getDepature() {
      return this.departure;
    }
    public Integer getDestination() {
      return this.destination;
    }
    public Boolean isEntered() {
      return entered;
    }
    public void setEntered(Boolean entered) {
      this.entered = entered;
    }
    public Integer getNumber() {
      return number;
    }
    public void setNumber(Integer number) {
      this.number = number;
    }
    public String toString() {
      return "number = "
          + this.number
          + " departure = "
          + this.departure
          + " destination = "
          + this.destination
          + " entered = "
          + this.entered;
    }
  }
}