motlin

Map<Color, Long> map =
    people.stream().collect(Collectors.groupingBy(
        Person::getFavoriteColor,
        Collectors.counting()));

motlin

Map<Color, List<Person>> map = people
    .stream()
    .collect(Collectors.groupingBy(Person::getFavoriteColor));

motlin

Map<Color, Set<Person>> map =
    people.stream().collect(Collectors.groupingBy(
        Person::getFavoriteColor,
        Collectors.toSet()));

motlin

MutableSetMultimap<Color, Person> multimap =
    people.groupBy(Person::getFavoriteColor);

motlin

MutableSet<Address> addresses = people.collect(Person::getAddress);

motlin

MutableSet<Person> people = ...;
MutableSet<Address> addresses = people
    .asLazy()
    .collect(Person::getAddress)
    .toSet();

motlin

Set<Person> people = ...;
Set<Address> addresses = people
    .stream()
    .map(Person::getAddress)
    .collect(Collectors.toSet());

motlin

public Option<V> get(Object key)
{
    V result = this.table.get(key);
    if (result == null && !this.table.containsKey(key))
    {
        return None.INSTANCE;
    }
    return new Some<V>(result);
}

motlin

public enum None implements Option<Nothing>
{
    INSTANCE;

    public Nothing get()
    {
        throw new UnsupportedOperationException("None.get()");
    }
}

motlin

undefined :: a
error :: [Char] -> a