<T> void clearReferenceQueue(ReferenceQueue<T> referenceQueue) {
      while (referenceQueue.poll() != null) {}
    }

    /** Returns first entry of bin for given hash. */
    @CheckForNull
    E getFirst(int hash) {
      // read this volatile field only once
      AtomicReferenceArray<E> table = this.table;
      return table.get(hash & (table.length() - 1));
    }

        }
    }

    @Override
    protected void writeHeaders(final HttpServletResponse response) {
        ComponentUtil.getFessConfig().getApiJsonResponseHeaderList().forEach(e -> response.setHeader(e.getFirst(), e.getSecond()));
    }

    protected void writeJsonResponse(final int status, final Throwable t) {
        final Supplier<String> stacktraceString = () -> {

   *
   * @throws NullPointerException if the first element is null; if this is a possibility, use {@code
   *     iterator().next()} or {@link Iterables#getFirst} instead.
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();

   *
   * @throws NullPointerException if the first element is null; if this is a possibility, use {@code
   *     iterator().next()} or {@link Iterables#getFirst} instead.
   */
  @SuppressWarnings("nullness") // Unsafe, but we can't do much about it now.
  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();

   * @return the first element of {@code iterable} or the default value
   * @since 7.0
   */
  @ParametricNullness
  public static <T extends @Nullable Object> T getFirst(
      Iterable<? extends T> iterable, @ParametricNullness T defaultValue) {
    return Iterators.getNext(iterable.iterator(), defaultValue);
  }

  /**

    }
  }

  /**
   * Returns the next element in {@code iterator} or {@code defaultValue} if the iterator is empty.
   * The {@link Iterables} analog to this method is {@link Iterables#getFirst}.
   *
   * @param defaultValue the default value to return if the iterator is empty
   * @return the next element of {@code iterator} or the default value
   * @since 7.0
   */
  @ParametricNullness

    }
  }

  /**
   * Returns the next element in {@code iterator} or {@code defaultValue} if the iterator is empty.
   * The {@link Iterables} analog to this method is {@link Iterables#getFirst}.
   *
   * @param defaultValue the default value to return if the iterator is empty
   * @return the next element of {@code iterator} or the default value
   * @since 7.0
   */
  @ParametricNullness

   * @return the first element of {@code iterable} or the default value
   * @since 7.0
   */
  @ParametricNullness
  public static <T extends @Nullable Object> T getFirst(
      Iterable<? extends T> iterable, @ParametricNullness T defaultValue) {
    return Iterators.getNext(iterable.iterator(), defaultValue);
  }

  /**

        if (weight > 0) {
          return e;
        }
      }
      throw new AssertionError();
    }

    /** Returns first entry of bin for given hash. */
    ReferenceEntry<K, V> getFirst(int hash) {
      // read this volatile field only once
      AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
      return table.get(hash & (table.length() - 1));
    }

        if (weight > 0) {
          return e;
        }
      }
      throw new AssertionError();
    }

    /** Returns first entry of bin for given hash. */
    ReferenceEntry<K, V> getFirst(int hash) {
      // read this volatile field only once
      AtomicReferenceArray<ReferenceEntry<K, V>> table = this.table;
      return table.get(hash & (table.length() - 1));
    }