*/
  public PatternFilenameFilter(Pattern pattern) {
    this.pattern = Preconditions.checkNotNull(pattern);
  }

  /*
   * Our implementation works fine with a null `dir`. However, there's nothing in the documentation
   * of the supertype that suggests that implementations are expected to tolerate null. That said, I
   * see calls in Google code that pass a null `dir` to a FilenameFilter.... So let's declare the

     * fastest possible implementation, which delegates to the array overload of String.join.
     *
     * In theory, we can quickly determine the size of any Collection. However, thanks to
     * regrettable implementations like our own Sets.filter, Collection.size() is sometimes a
     * linear-time operation, and it can even have side effects. Thus, we limit the special case to

 * a little different from those of other Collection-related features such as {@link
 * CollectionFeature} or {@link SetFeature}.
 *
 * <p>However, when {@link CollectionSize.Require} is used to annotate a test it behaves normally
 * (i.e. it requires the collection instance under test to be a certain size for the test to run).

 * a little different from those of other Collection-related features such as {@link
 * CollectionFeature} or {@link SetFeature}.
 *
 * <p>However, when {@link CollectionSize.Require} is used to annotate a test it behaves normally
 * (i.e. it requires the collection instance under test to be a certain size for the test to run).

 * information</i>.
 *
 * <h3>Invertibility</h3>
 *
 * <p>The reverse operation <b>may</b> be a strict <i>inverse</i> (meaning that {@code
 * converter.reverse().convert(converter.convert(a)).equals(a)} is always true). However, it is very
 * common (perhaps <i>more</i> common) for round-trip conversion to be <i>lossy</i>. Consider an
 * example round-trip using {@link com.google.common.primitives.Doubles#stringConverter}:
 *
 * <ol>

   * the Android flavor of Guava). The field is declared with a type of {@code Object} to avoid
   * compatibility problems on Android VMs. The corresponding accessor method, however, can have the
   * more specific return type as long as users are careful to guard calls to it with version checks
   * or reflection: Android VMs ignore the types of elements that aren't used.
   */

   * the backport does. For now, we're keeping the class declaration in *both* flavors so that both
   * flavors can read old data or data from the other flavor. However, we strongly discourage
   * relying on this, as we have made incompatible changes to serialized forms in the past and
   * expect to do so again, as discussed in https://github.com/google/guava#important-warnings.
   */

 - **CacheHit**
 - ConnectionReleased
 - CallEnd
 
## Cache directory

The cache directory must be exclusively owned by a single instance.

Deleting the cache when it is no longer needed can be done.  However this may delete the purpose of the cache
which is designed to persist between app restarts.

```kotlin
cache.delete()
```
 
## Pruning the Cache

   *
   * <p>Historically, {@code Supplier} instances in this library have implemented this method to
   * recognize certain cases where distinct {@code Supplier} instances would in fact behave
   * identically. However, as code migrates to {@code java.util.function}, that behavior will
   * disappear. It is best not to depend on it.
   */
  @Override
  boolean equals(@Nullable Object object);

   * add the suppression to the whole method (which turns off checking for a large section of code),
   * or extract a variable, and put the suppression on that. However, a local variable typically
   * doesn't work: Because nullness analyses typically infer the nullness of local variables,
   * there's no way to assign a {@code @Nullable T} to a field {@code T foo;} and instruct the