116. Getting a list from a stream

Collecting a Stream into a List is a popular task that occurs all over the place in applications that manipulate streams and collections.

In JDK 8, collecting a Stream into a List can be done via the toList() collector as follows:

List<File> roots = Stream.of(File.listRoots())
  .collect(Collectors.toList());

Starting with JDK 10, we can rely on the toUnmodifiableList() collector (for maps, use toUnmodifiableMap(), and for sets, toUnmodifiableSet()):

List<File> roots = Stream.of(File.listRoots())
  .collect(Collectors.toUnmodifiableList());

Obviously, the returned list is an unmodifiable/immutable list.

JDK 16 has introduced the following toList() default method in the Stream interface:

default List<T> toList() {
  return (List<T>) Collections.unmodifiableList(
    new ArrayList<>(Arrays.asList(this.toArray())));
}

Using this method to collect a Stream into an unmodifiable/immutable...