*
   * @param string the string to test and possibly return
   * @return {@code string} if it is not null; {@code ""} otherwise
   */
  static String nullToEmpty(@Nullable String string) {
    return (string == null) ? "" : string;
  }

  /**
   * Returns the string if it is not empty, or a null string otherwise.
   *
   * @param string the string to test and possibly return

    }

    private static final Logger log = LoggerFactory.getLogger(RdmaProviderFactory.class);

    /**
     * Create RDMA provider based on preference string
     *
     * @param preference provider preference ("auto", "disni", "tcp", etc.)
     * @return best available RDMA provider, or null if none available
     */
    public static RdmaProvider createProvider(String preference) {

     * Gets the platform tool executable.
     *
     * @param toolName the tool platform independent tool name
     * @return file representing the tool executable, or null if the tool cannot be found
     */
    String findTool(String toolName);

    /**
     * Let the toolchain decide if it matches requirements defined
     * in the toolchain plugin configuration.
     *
     * @param requirements key value pair, may not be {@code null}

接著你可以在模型屬性上使用 `Field`：

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[11:14] *}

`Field` 的用法與 `Query`、`Path`、`Body` 相同，擁有相同的參數等。

/// note | 技術細節

實際上，你接下來會看到的 `Query`、`Path` 等，會建立共同父類別 `Param` 的子類別物件，而 `Param` 本身是 Pydantic 的 `FieldInfo` 類別的子類別。

而 Pydantic 的 `Field` 也會回傳一個 `FieldInfo` 的實例。

`Body` 也會直接回傳 `FieldInfo` 子類別的物件。稍後你會看到還有其他類別是 `Body` 類別的子類別。

記得，當你從 `fastapi` 匯入 `Query`、`Path` 等時，它們其實是回傳特殊類別的函式。

///

   * {@link #isWellFormed(byte[])}. Note that this can be false even when {@code
   * isWellFormed(bytes)} is true.
   *
   * @param bytes the input buffer
   * @param off the offset in the buffer of the first byte to read
   * @param len the number of bytes to read from the buffer
   */
  public static boolean isWellFormed(byte[] bytes, int off, int len) {
    int end = off + len;

   * {@link #isWellFormed(byte[])}. Note that this can be false even when {@code
   * isWellFormed(bytes)} is true.
   *
   * @param bytes the input buffer
   * @param off the offset in the buffer of the first byte to read
   * @param len the number of bytes to read from the buffer
   */
  public static boolean isWellFormed(byte[] bytes, int off, int len) {
    int end = off + len;

   * Registers all subscriber methods on {@code object} to receive events.
   *
   * @param object object whose subscriber methods should be registered.
   */
  public void register(Object object) {
    subscribers.register(object);
  }

  /**
   * Unregisters all subscriber methods on a registered {@code object}.
   *
   * @param object object whose subscriber methods should be unregistered.

   *
   * <p>The default implementation iterates over the sequence in forward order, beginning at {@code
   * start}, calling {@link #matches} for each character.
   *
   * @param sequence the character sequence to examine
   * @param start the first index to examine; must be nonnegative and no greater than {@code
   *     sequence.length()}

@NullMarked
public abstract class IteratorTester<E extends @Nullable Object>
    extends AbstractIteratorTester<E, Iterator<E>> {
  /**
   * Creates an IteratorTester.
   *
   * @param steps how many operations to test for each tested pair of iterators
   * @param features the features supported by the iterator
   */
  protected IteratorTester(
      int steps,
      Iterable<? extends IteratorFeature> features,

 * CollectionSize} present in the features specified by {@link #withFeatures(Feature...)}.
 *
 * @param <B> The concrete type of this builder (the 'self-type'). All the Builder methods of this
 *     class (such as {@link #named(String)}) return this type, so that Builder methods of more
 *     derived classes can be chained onto them without casting.
 * @param <G> The type of the generator to be passed to testers in the generated test suite. An