*
   * @since 33.2.0 (available since 21.0 in guava-jre)
   */
  @SuppressWarnings({"AndroidJdkLibsChecker", "Java7ApiChecker"})
  @IgnoreJRERequirement // Users will use this only if they're already using streams.
  @Beta // TODO: b/288085449 - Remove.
  public static <E extends Enum<E>> Collector<E, ?, ImmutableSet<E>> toImmutableEnumSet() {

   * throws an {@code IllegalStateException}.)
   *
   * @since 33.2.0 (available since 21.0 in guava-jre)
   */
  @SuppressWarnings({"AndroidJdkLibsChecker", "Java7ApiChecker"})
  @IgnoreJRERequirement // Users will use this only if they're already using streams.
  @Beta // TODO: b/288085449 - Remove.
  public static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableSortedMap<K, V>> toImmutableSortedMap(

        // getDeclaredField to throw a NoSuchFieldException when the field is definitely there.
        // For these users fallback to a suboptimal implementation, based on synchronized. This will
        // be a definite performance hit to those users.
        thrownAtomicReferenceFieldUpdaterFailure = atomicReferenceFieldUpdaterFailure;
        helper = new SynchronizedHelper();
      }
    }

       * template to be null (though we do handle that case gracefully at runtime). I've left this
       * one as it is because one of our users has defined a wrapper API around Preconditions,
       * declaring a checkState method that accepts a possibly null template. So we'd need to update
       * that user first.
       */
      @CheckForNull String errorMessageTemplate,
      @CheckForNull @Nullable Object... errorMessageArgs) {

 *
 * <p><b>Note:</b> by default, the returned cache uses equality comparisons (the {@link
 * Object#equals equals} method) to determine equality for keys or values. However, if {@link
 * #weakKeys} was specified, the cache uses identity ({@code ==}) comparisons instead for keys.
 * Likewise, if {@link #weakValues} or {@link #softValues} was specified, the cache uses identity
 * comparisons for values.
 *

   * @Nullable X>, then users might pass a TypeParameter<Y>, where Y is a subtype of X, while still
   * passing a TypeToken<X>. This would be invalid. Maybe we could accept a TypeParameter<@PolyNull
   * X> if we support such a thing? It would be weird or misleading for users to be able to pass
   * `new TypeParameter<@Nullable T>() {}` and have it act as a plain `TypeParameter<T>`, but

      Iterator<? extends T> iterator) {
    if (iterator instanceof PeekingImpl) {
      // Safe to cast <? extends T> to <T> because PeekingImpl only uses T
      // covariantly (and cannot be subclassed to add non-covariant uses).
      @SuppressWarnings("unchecked")
      PeekingImpl<T> peeking = (PeekingImpl<T>) iterator;
      return peeking;
    }
    return new PeekingImpl<>(iterator);
  }

      Iterator<? extends T> iterator) {
    if (iterator instanceof PeekingImpl) {
      // Safe to cast <? extends T> to <T> because PeekingImpl only uses T
      // covariantly (and cannot be subclassed to add non-covariant uses).
      @SuppressWarnings("unchecked")
      PeekingImpl<T> peeking = (PeekingImpl<T>) iterator;
      return peeking;
    }
    return new PeekingImpl<>(iterator);
  }

       * template to be null (though we do handle that case gracefully at runtime). I've left this
       * one as it is because one of our users has defined a wrapper API around Preconditions,
       * declaring a checkState method that accepts a possibly null template. So we'd need to update
       * that user first.
       */
      @CheckForNull String errorMessageTemplate,
      @CheckForNull @Nullable Object... errorMessageArgs) {

    /*
     * Another way to express this signature would be to bound <V> by @NonNull and accept
     * LF<? extends @Nullable V>. That might be better: There's currently no difference between the
     * outputs users get when calling this with <Foo> and calling it with <@Nullable Foo>. The only
     * difference is that calling it with <Foo> won't work when an input Future has a @Nullable