terminal.java

Optional<Integer> minAge = person
                              .stream()
                              .map(p -> p.getAge()) // return Stream<Integer>
                              .filter(age -> age > 20) // return Stream<Integer>
                              .min(Comparator.naturalOrder()); // terminal operation

people.stream()
      .map(p -> p.getLastname())
      .allMatch(length < 10); // terminal operation