if (field == null && started) {
        field = ServerSocketFactory.getDefault() // Build the default value lazily.
      }
      return field
    }

    @Synchronized set(value) {
      check(!started) { "serverSocketFactory must not be set after start()" }
      field = value
    }

  private var serverSocket: ServerSocket? = null
  private var sslSocketFactory: SSLSocketFactory? = null

## 선택적 매개변수

같은 방법으로 기본값을 `None`으로 설정하여 선택적 매개변수를 선언할 수 있습니다:

```Python hl_lines="9"
{!../../docs_src/query_params/tutorial002.py!}
```

이 경우 함수 매개변수 `q`는 선택적이며 기본값으로 `None` 값이 됩니다.

/// check | "확인"

**FastAPI**는 `item_id`가 경로 매개변수이고 `q`는 경로 매개변수가 아닌 쿼리 매개변수라는 것을 알 정도로 충분히 똑똑합니다.

///

/// note | "참고"

FastAPI는 `q`가 `= None`이므로 선택적이라는 것을 인지합니다.

		debug.PrintStack()
		return metacache{}
	}

	// Grab a write lock, since we create one if we cannot find one.
	b.mu.Lock()
	defer b.mu.Unlock()

	// Check if exists already.
	if c, ok := b.caches[o.ID]; ok {
		c.lastHandout = time.Now()
		b.caches[o.ID] = c
		b.debugf("returning existing %v", o.ID)
		return c
	}

	if !o.Create {
		return metacache{

   * @return the escaped form of {@code string}
   * @throws NullPointerException if {@code string} is null
   */
  @Override
  public String escape(String string) {
    checkNotNull(string); // GWT specific check (do not optimize)
    // Inlineable fast-path loop which hands off to escapeSlow() only if needed
    int length = string.length();
    for (int index = 0; index < length; index++) {

import org.codehaus.plexus.logging.Logger;
import org.eclipse.aether.ConfigurationProperties;
import org.eclipse.aether.util.ConfigUtils;

// TODO remove the update check manager
// TODO separate into retriever and publisher
// TODO remove hardcoding of checksum logic

/**
 * Manages <a href="https://maven.apache.org/wagon">Wagon</a> related operations in Maven.
 */
@Named

```Python hl_lines="21"
{!../../docs_src/path_operation_configuration/tutorial005.py!}
```

/// info | "情報"

`respnse_description`は具体的にレスポンスを参照し、`description`は*path operation*全般を参照していることに注意してください。

///

/// check | "確認"

OpenAPIは*path operation*ごとにレスポンスの説明を必要としています。

そのため、それを提供しない場合は、**FastAPI** が自動的に「成功のレスポンス」を生成します。

///

<img src="https://fastapi.tiangolo.com/img/tutorial/path-operation-configuration/image03.png">

    return asImmutableList(array);
  }

  /** Views the array as an immutable list. Checks for nulls; does not copy. */
  private static <E> ImmutableList<E> construct(Object... elements) {
    return asImmutableList(checkElementsNotNull(elements));
  }

  /**
   * Views the array as an immutable list. Does not check for nulls; does not copy.
   *
   * <p>The array must be internally created.
   */

		vc, err = globalBucketVersioningSys.Get(bucket)
		if err != nil {
			return err
		}

		// Check if the current bucket has a configured lifecycle policy
		lc, err = globalLifecycleSys.Get(bucket)
		if err != nil && !errors.Is(err, BucketLifecycleNotFound{Bucket: bucket}) {
			return err
		}

		// Check if bucket is object locked.
		lr, err = globalBucketObjectLockSys.Get(bucket)
		if err != nil {
			return err

			}
		}
	}
}

// Helpers for tests.

// Check if two `mountInfo` are equal.
func mountPointsEqual(a, b mountInfo) bool {
	if a.Device != b.Device || a.Path != b.Path || a.FSType != b.FSType || !slicesEqual(a.Options, b.Options) || a.Pass != b.Pass || a.Freq != b.Freq {
		return false
	}
	return true
}

// Checks if two string slices are equal.
func slicesEqual(a, b []string) bool {

    // Check the user response. It has the application's original request.
    cacheMiss.assertCode(200)
      .assertBody("B")
      .assertHeader("Donut", "b")
      .assertRequestUrl(server.url("/"))
      .assertSentRequestAtMillis(request2SentAt, request2ReceivedAt)
      .assertReceivedResponseAtMillis(request2SentAt, request2ReceivedAt)