return pickInstance(Currency.getAvailableCurrencies(), Currency.getInstance(Locale.US));
  }

  @Empty
  <T> Optional<T> generateJavaOptional() {
    return Optional.empty();
  }

  @Generates
  <T> Optional<T> generateJavaOptional(T value) {
    return Optional.of(value);
  }

  @Generates
  OptionalInt generateOptionalInt() {
    return OptionalInt.of(generateInt());
  }

本例中，查询参数 `q` 是可选的，默认值为 `None`。

/// check | 检查

注意，**FastAPI** 可以识别出 `item_id` 是路径参数，`q` 不是路径参数，而是查询参数。

///

/// note | 笔记

因为默认值为 `= None`，FastAPI 把 `q` 识别为可选参数。

FastAPI 不使用 `Optional[str]` 中的 `Optional`（只使用 `str`），但 `Optional[str]` 可以帮助编辑器发现代码中的错误。

///

## 查询参数类型转换

参数还可以声明为 `bool` 类型，FastAPI 会自动转换参数类型：


{* ../../docs_src/query_params/tutorial003_py310.py hl[7] *}

本例中，访问：

```

   * Returns a composite adapter for a struct or data class. This may be used for both SEQUENCE and
   * SET types.
   *
   * The fields are specified as a list of member adapters. When decoding, a value for each
   * non-optional member but be included in sequence.
   *
   * TODO: for sets, sort by tag when encoding.
   * TODO: for set ofs, sort by encoded value when encoding.
   */
  fun <T> sequence(
    name: String,

   * implementations.
   */
  SUPPORTS_SET;

  /**
   * A set containing none of the optional features of the {@link Iterator} or {@link ListIterator}
   * interfaces.
   */
  public static final Set<IteratorFeature> UNMODIFIABLE = emptySet();

  /**
   * A set containing all of the optional features of the {@link Iterator} and {@link ListIterator}
   * interfaces.
   */

                        .nonRecursive()
                        .expectResult(MODULE_C),
                scenario("Selected optional project")
                        .activeOptionalProjects(MODULE_B)
                        .expectResult(MODULE_B),
                scenario("Selected missing optional project")
                        .activeOptionalProjects("non-existing-module")
                        .expectResult(

     * @see org.apache.maven.api.services.ArtifactManager#getPath(Artifact)
     */
    @Nonnull
    default Optional<ProducedArtifact> getMainArtifact() {
        List<ProducedArtifact> artifacts = getArtifacts();
        return artifacts.size() == 2 ? Optional.of(artifacts.get(1)) : Optional.empty();
    }

    /**

			Key:         config.SubnetSubSys,
			Type:        "string",
			Description: "register Enterprise license for the cluster",
			Optional:    true,
		},
		config.HelpKV{
			Key:         config.CallhomeSubSys,
			Type:        "string",
			Description: "enable callhome to MinIO SUBNET",
			Optional:    true,
		},
		config.HelpKV{
			Key:         config.DriveSubSys,
			Description: "enable drive specific settings",
		},

import org.codelibs.fess.opensearch.config.exentity.WebConfig;
import org.codelibs.fess.util.ComponentUtil;
import org.codelibs.fess.util.RenderDataUtil;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.Execute;
import org.lastaflute.web.response.HtmlResponse;
import org.lastaflute.web.response.render.RenderData;

import org.codelibs.fess.opensearch.config.exentity.KeyMatch;
import org.codelibs.fess.util.ComponentUtil;
import org.codelibs.fess.util.RenderDataUtil;
import org.dbflute.optional.OptionalEntity;
import org.dbflute.optional.OptionalThing;
import org.lastaflute.web.Execute;
import org.lastaflute.web.response.HtmlResponse;
import org.lastaflute.web.response.render.RenderData;

    /**
     * The network name of the share.
     */
    protected String netName;
    /**
     * The type of the share (e.g., disk, printer, IPC).
     */
    protected int type;
    /**
     * The optional comment or description for the share.
     */
    protected String remark;

    /**
     * Default constructor for SmbShareInfo.
     */
    public SmbShareInfo() {
    }

    /**