*   <li>{@link Lists}
 *   <li>{@link Maps}
 *   <li>{@link MoreCollectors}
 *   <li>{@link Multimaps}
 *   <li>{@link Multisets}
 *   <li>{@link ObjectArrays}
 *   <li>{@link Queues}
 *   <li>{@link Sets}
 *   <li>{@link Streams}
 *   <li>{@link Tables}
 * </ul>
 *
 * <h2>Abstract implementations</h2>
 *
 * <ul>
 *   <li>{@link AbstractIterator}
 *   <li>{@link AbstractSequentialIterator}

      return emptySet();
    } else {
      return emptyList();
    }
  }

  @Override
  public void clear() {
    keySet().clear();
  }

  @Override
  Set<K> createKeySet() {
    return Sets.filter(unfiltered.keySet(), keyPredicate);
  }

  @Override
  public Collection<V> get(@ParametricNullness K key) {
    if (keyPredicate.apply(key)) {
      return unfiltered.get(key);

			}

			// Enable TCP open
			// https://lwn.net/Articles/508865/ - 32k queue size.
			_ = syscall.SetsockoptInt(fd, syscall.SOL_TCP, unix.TCP_FASTOPEN, 32*1024)

			// Enable TCP fast connect
			// TCPFastOpenConnect sets the underlying socket to use
			// the TCP fast open connect. This feature is supported
			// since Linux 4.11.
			_ = syscall.SetsockoptInt(fd, syscall.IPPROTO_TCP, unix.TCP_FASTOPEN_CONNECT, 1)

    public void delete(final RequestHeader requestHeader) {

        requestHeaderBhv.delete(requestHeader, op -> {
            op.setRefreshPolicy(Constants.TRUE);
        });

    }

    /**
     * Sets up the database query conditions for retrieving request headers based on pager criteria.
     *
     * @param cb the condition bean for building the database query

     * "java.protocol.handler.pkgs".
     */
    private static final String[] JVM_VENDOR_DEFAULT_PKGS = { "sun.net.www.protocol" };

    private static URLStreamHandlerFactory factory;

    /**
     * Sets the URL stream handler factory for the environment.  This
     * allows specification of the factory used in creating underlying
     * stream handlers.  This can be called once per JVM instance.
     *

	"github.com/minio/minio/internal/mcontext"

	xhttp "github.com/minio/minio/internal/http"
)

const contextAuditKey = contextKeyType("audit-entry")

// SetAuditEntry sets Audit info in the context.
func SetAuditEntry(ctx context.Context, audit *audit.Entry) context.Context {
	if ctx == nil {
		LogIf(context.Background(), "audit", fmt.Errorf("context is nil"))
		return nil
	}

* `expose_headers` - Indicate any response headers that should be made accessible to the browser. Defaults to `[]`.
* `max_age` - Sets a maximum time in seconds for browsers to cache CORS responses. Defaults to `600`.

The middleware responds to two particular types of HTTP request...

### CORS preflight requests { #cors-preflight-requests }

	sys.hMutex.RLock()
	defer sys.hMutex.RUnlock()
	if h, ok := sys.hc[ep.Host]; ok {
		return !h.Online
	}
	go sys.initHC(ep)
	return false
}

// markOffline sets endpoint to offline if network i/o timeout seen.
func (sys *BucketTargetSys) markOffline(ep *url.URL) {
	sys.hMutex.Lock()
	defer sys.hMutex.Unlock()
	if h, ok := sys.hc[ep.Host]; ok {
		h.Online = false

	// Put all buckets into channel.
	bucketCh := make(chan BucketInfo, len(buckets))

	// Shuffle buckets to ensure total randomness of buckets, being scanned.
	// Otherwise same set of buckets get scanned across erasure sets always.
	// at any given point in time. This allows different buckets to be scanned
	// in different order per erasure set, this wider spread is needed when
	// there are lots of buckets with different order of objects in them.

 *
 * <p>If the values corresponding to a single key should be ordered according to a {@link
 * java.util.Comparator} (or the natural order), see the {@link SortedSetMultimap} subinterface.
 *
 * <p>Since the value collections are sets, the behavior of a {@code SetMultimap} is not specified
 * if key or value objects already present in the multimap change in a manner that affects