* task cannot be implemented with {@link ListeningExecutorService}, the various {@link Futures}
 * utility methods, or {@link ListenableFutureTask}. Those APIs have less opportunity for developer
 * error. If your needs are more complex than {@code SettableFuture} supports, use {@link
 * AbstractFuture}, which offers an extensible version of the API.
 *
 * @author Sven Mawson

  }

  // Overriding to mark it Nullable
  @Override
  @CheckForNull
  public abstract V get(@CheckForNull Object key);

  /**
   * {@inheritDoc}
   *
   * <p>See <a
   * href="https://developer.android.com/reference/java/util/Map.html#getOrDefault%28java.lang.Object,%20V%29">{@code
   * Map.getOrDefault}</a>.
   *
   * @since 23.5 (but since 21.0 in the JRE <a

 *       initialize all possible subscribers at startup time.
 *   <li>It uses reflection in ways that break when code is processed by optimizers/minimizers like
 *       <a href="https://developer.android.com/studio/build/shrink-code">R8 and Proguard</a>.
 *   <li>It doesn't offer a way to wait for multiple events before taking action. For example, it

  /**
   * The HTTP <a
   * href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Link_prefetching_FAQ#As_a_server_admin.2C_can_I_distinguish_prefetch_requests_from_normal_requests.3F">{@code
   * Purpose}</a> header field name.
   *
   * @since 28.0
   */
  public static final String PURPOSE = "Purpose";
  /**
   * The HTTP <a

   * nullness checker can already "prove" are non-null. That means that the first parameter to
   * checkNotNull *should* be annotated to require it to be non-null.
   *
   * However, for a variety of reasons, Google developers have written a ton of code over the past
   * decade that assumes that they can use checkNotNull for non-precondition checks. I had hoped to

 * systems and high-level APIs that provide autoescaping.
 * One Google-authored templating system available for external use is <a
 * href="https://developers.google.com/closure/templates/">Closure Templates</a>.
 *
 * <p>HTML escaping is particularly tricky: For example, <a href="http://goo.gl/5TgZb">some

 *       annotations in Guava. Or you might prefer to omit Guava from your {@code AnnotatedPackages}
 *       list.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>
 *   <li>{@code NullPointerTester}, at least in the Android backport (where the type-use annotations
 *       {@code NullPointerTester} would need are not available) and in case of <a

 *       annotations in Guava. Or you might prefer to omit Guava from your {@code AnnotatedPackages}
 *       list.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>
 *   <li>{@code NullPointerTester}, at least in the Android backport (where the type-use annotations
 *       {@code NullPointerTester} would need are not available) and in case of <a

 *       annotations in Guava. Or you might prefer to omit Guava from your {@code AnnotatedPackages}
 *       list.
 *   <li><a href="https://developers.google.com/j2objc">J2ObjC</a>
 *   <li>{@code NullPointerTester}, at least in the Android backport (where the type-use annotations
 *       {@code NullPointerTester} would need are not available) and in case of <a

   *     not support creating temporary directories securely
   * @deprecated For Android users, see the <a
   *     href="https://developer.android.com/training/data-storage" target="_blank">Data and File
   *     Storage overview</a> to select an appropriate temporary directory (perhaps {@code