@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
   *     href="https://github.com/google/guava#guava-google-core-libraries-for-java">flavor</a>).