* iterable is empty.
   *
   * <p><b>Java 8+ users:</b> the {@code Stream} equivalent to this method is {@code
   * stream.collect(MoreCollectors.toOptional()).orElse(defaultValue)}.
   *
   * @throws IllegalArgumentException if the iterator contains multiple elements
   */
  @ParametricNullness
  public static <T extends @Nullable Object> T getOnlyElement(

   * iterable is empty.
   *
   * <p><b>Java 8+ users:</b> the {@code Stream} equivalent to this method is {@code
   * stream.collect(MoreCollectors.toOptional()).orElse(defaultValue)}.
   *
   * @throws IllegalArgumentException if the iterator contains multiple elements
   */
  @ParametricNullness
  public static <T extends @Nullable Object> T getOnlyElement(

   *
   * <p><b>Java 9 users:</b> use {@code optional.stream()} instead.
   */
  @Beta
  @InlineMe(replacement = "optional.stream()")
  @InlineMeValidationDisabled("Java 9+ API only")
  public static <T> Stream<T> stream(java.util.Optional<T> optional) {
    return optional.isPresent() ? Stream.of(optional.get()) : Stream.empty();
  }

  /**
   * If a value is present in {@code optional}, returns a stream containing only that element,

  }

  private static final Function<Object, Optional<?>> NULLABLE_TO_OPTIONAL =
      new Function<Object, Optional<?>>() {
        @Override
        public Optional<?> apply(@Nullable Object obj) {
          return Optional.fromNullable(obj);
        }
      };

  private static final Function<Optional<?>, @Nullable Object> OPTIONAL_TO_NULLABLE =
      new Function<Optional<?>, @Nullable Object>() {
        @Override

  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();
    return iterator.hasNext() ? Optional.of(iterator.next()) : Optional.absent();
  }

  /**
   * Returns an {@link Optional} containing the last element in this fluent iterable. If the
   * iterable is empty, {@code Optional.absent()} is returned. If the underlying {@code iterable} is

  public final Optional<@NonNull E> first() {
    Iterator<E> iterator = getDelegate().iterator();
    return iterator.hasNext() ? Optional.of(iterator.next()) : Optional.absent();
  }

  /**
   * Returns an {@link Optional} containing the last element in this fluent iterable. If the
   * iterable is empty, {@code Optional.absent()} is returned. If the underlying {@code iterable} is

import org.codelibs.fess.util.ComponentUtil;
import org.codelibs.fess.util.DocumentUtil;
import org.codelibs.fess.util.FacetResponse;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.util.LaRequestUtil;
import org.opensearch.action.search.SearchRequestBuilder;
import org.opensearch.action.search.SearchResponse;

		<dependency>
			<groupId>org.slf4j</groupId>
			<artifactId>slf4j-api</artifactId>
			<version>1.7.26</version>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>commons-logging</groupId>
			<artifactId>commons-logging</artifactId>
			<version>1.3.5</version>
			<optional>true</optional>
		</dependency>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>

    }

    @Override
    public Optional<Long> lengthIfKnown() {
      long result = 0L;
      for (CharSource source : sources) {
        Optional<Long> lengthIfKnown = source.lengthIfKnown();
        if (!lengthIfKnown.isPresent()) {
          return Optional.absent();
        }
        result += lengthIfKnown.get();
      }
      return Optional.of(result);
    }

    @Override

    }

    @Override
    public Optional<Long> lengthIfKnown() {
      long result = 0L;
      for (CharSource source : sources) {
        Optional<Long> lengthIfKnown = source.lengthIfKnown();
        if (!lengthIfKnown.isPresent()) {
          return Optional.absent();
        }
        result += lengthIfKnown.get();
      }
      return Optional.of(result);
    }

    @Override