*     this.codes = ImmutableSet.copyOf(codes);
 *     checkArgument(Collections.disjoint(this.codes, RESERVED_CODES));
 *   }
 * }
 * }
 *
 * <h3>See also</h3>
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained">immutable collections</a>.
 *
 * @since 2.0
 */
@DoNotMock("Use ImmutableList.of or another implementation")
@GwtCompatible

 *
 * {@snippet :
 * // Bad! Do not do this!
 * Joiner joiner = Joiner.on(',');
 * joiner.skipNulls(); // does nothing!
 * return joiner.join("wrong", null, "wrong");
 * }
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/StringsExplained#joiner">{@code Joiner}</a>.
 *
 * @author Kevin Bourrillion
 * @since 2.0
 */
@GwtCompatible
public class Joiner {

Затем с `random.choice()` можно получить **случайное значение** из списка — то есть кортеж вида `(id, name)`. Это будет что‑то вроде `("imdb-tt0371724", "The Hitchhiker's Guide to the Galaxy")`.

После этого мы **распаковываем** эти два значения кортежа в переменные `id` и `name`.

Так что, если пользователь не передал ID элемента, он всё равно получит случайную рекомендацию.

import org.jspecify.annotations.Nullable;

/**
 * A {@link List} whose contents will never change, with many other important properties detailed at
 * {@link ImmutableCollection}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/ImmutableCollectionsExplained">immutable collections</a>.
 *
 * @see ImmutableMap
 * @see ImmutableSet
 * @author Kevin Bourrillion
 * @since 2.0
 */

 * either {@link Character} or {@link Arrays}.
 *
 * <p>All the operations in this class treat {@code char} values strictly numerically; they are
 * neither Unicode-aware nor locale-dependent.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
 *
 * @author Kevin Bourrillion
 * @since 1.0
 */
@GwtCompatible
public final class Chars {

import org.jspecify.annotations.Nullable;

/**
 * Static utility methods pertaining to {@code short} primitives, that are not already found in
 * either {@link Short} or {@link Arrays}.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
 *
 * @author Kevin Bourrillion
 * @since 1.0
 */
@GwtCompatible

 * read operations will work correctly. To allow concurrent update operations, wrap your multimap
 * with a call to {@link Multimaps#synchronizedListMultimap}.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multimap">{@code Multimap}</a>.
 *
 * @author Mike Bostock
 * @since 2.0
 */
@GwtCompatible

import org.jspecify.annotations.Nullable;

/**
 * Static utility methods pertaining to {@code short} primitives, that are not already found in
 * either {@link Short} or {@link Arrays}.
 *
 * <p>See the Guava User Guide article on <a
 * href="https://github.com/google/guava/wiki/PrimitivesExplained">primitive utilities</a>.
 *
 * @author Kevin Bourrillion
 * @since 1.0
 */
@GwtCompatible

Para OAuth2 son solo strings.

///

## Vista global { #global-view }

Primero, echemos un vistazo rápido a las partes que cambian desde los ejemplos en el **Tutorial - User Guide** principal para [OAuth2 con Password (y hashing), Bearer con tokens JWT](../../tutorial/security/oauth2-jwt.md){.internal-link target=_blank}. Ahora usando scopes de OAuth2:

  /**
   * NaCl applications. For more information see <a
   * href="https://developer.chrome.com/native-client/devguide/coding/application-structure">the
   * Developer Guide for Native Client Application Structure</a>.
   *
   * @since 20.0
   */
  public static final MediaType NACL_APPLICATION = createConstant(APPLICATION_TYPE, "x-nacl");

  /**