* don't invoke interruptTask.
             */
            false);
      }
    }
  }

  // TODO(lukes): investigate using the @Contended annotation on these fields when jdk8 is
  // available.
  /**
   * This field encodes the current state of the future.
   *
   * <p>The valid values are:
   *
   * <ul>
   *   <li>{@code null} initial state, nothing has happened.

    ImmutableSet.Builder<Field> builder = ImmutableSet.builder();
    for (Field field : cls.getDeclaredFields()) {
      /*
       * Coverage mode generates synthetic fields.  If we ever add private
       * fields, they will cause similar problems, and we may want to switch
       * this check to isAccessible().
       */
      if (!field.isSynthetic() && field.getType() == String.class) {
        builder.add(field);

 *
 * @author Kurt Alfred Kluever
 * @since 11.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class HttpHeaders {
  private HttpHeaders() {}

  // HTTP Request and Response header fields

  /** The HTTP {@code Cache-Control} header field name. */
  public static final String CACHE_CONTROL = "Cache-Control";
  /** The HTTP {@code Content-Length} header field name. */

   * value is null and {@link Object#equals} returns {@code true}. {@link Equivalence#hash} returns
   * {@code 0} if passed a null value.
   *
   * @since 13.0
   * @since 8.0 (in Equivalences with null-friendly behavior)
   * @since 4.0 (in Equivalences)
   */
  public static Equivalence<Object> equals() {
    return Equals.INSTANCE;
  }

  /**