* example round-trip using {@link com.google.common.primitives.Doubles#stringConverter}:
 *
 * <ol>
 *   <li>{@code stringConverter().convert("1.00")} returns the {@code Double} value {@code 1.0}
 *   <li>{@code stringConverter().reverse().convert(1.0)} returns the string {@code "1.0"} --
 *       <i>not</i> the same string ({@code "1.00"}) we started with
 * </ol>
 *

///

### 理解这段代码 { #understand-that-code }

关键点仅仅是：在 `Annotated` 中使用带函数的 **`AfterValidator`**。不感兴趣可以跳过这一节。🤸

---

但如果你对这个具体示例好奇，并且还愿意继续看，这里有一些额外细节。

#### 字符串与 `value.startswith()` { #string-with-value-startswith }

注意到了吗？字符串的 `value.startswith()` 可以接收一个元组，它会检查元组中的每个值：

{* ../../docs_src/query_params_str_validations/tutorial015_an_py310.py ln[16:19] hl[17] *}

#### 一个随机条目 { #a-random-item }

                allowEmpty = true,
            )
            text(
                "confirmationCode",
                "",
                label = "Confirmation Code",
                description = "Enter the value 'startCycle' (no quotes) to confirm the promotion",
                display = ParameterDisplay.PROMPT,
                allowEmpty = false,
            )
            text(
                "gitUserName",
                "",

  public Set<Feature<? super Multimap>> getImpliedFeatures() {
    return implied;
  }

  @Retention(RetentionPolicy.RUNTIME)
  @Inherited
  @TesterAnnotation
  public @interface Require {
    MultimapFeature[] value() default {};

    MultimapFeature[] absent() default {};
  }

 * <p>
 * Example of creating a custom qualifier:
 * <pre>
 * {@literal @}Qualifier
 * {@literal @}Retention(RUNTIME)
 * public @interface Database {
 *     String value();
 * }
 * </pre>
 *
 * @see Named
 * @since 4.0.0
 */
@Target(ANNOTATION_TYPE)
@Retention(RUNTIME)
@Documented

public interface ToolchainPrivate extends Toolchain {

    /**
     * Let the toolchain decide if it matches requirements defined
     * in the toolchain plugin configuration.
     * @param requirements Map<String, String> key value pair, may not be {@code null}
     * @return {@code true} if the requirements match, otherwise {@code false}
     */
    boolean matchesRequirements(Map<String, String> requirements);

    /**
     *

    algorithms.find {
      it.encoding.equals(encoding, ignoreCase = true)
    }

  /**
   * A decompression algorithm such as Gzip. Must provide the Accept-Encoding value and decompress a Source.
   */
  interface DecompressionAlgorithm {
    val encoding: String

    fun decompress(compressedSource: BufferedSource): Source
  }

    // request headers.
    // 431 "Request Header Fields Too Large"
    val largeHeaders =
      Headers
        .Builder()
        .apply {
          repeat(32) {
            add("name-$it", "value-$it-" + "0".repeat(1024))
          }
        }.build()
    val call2 =
      client.newCall(
        Request
          .Builder()
          .url(server.url("/"))
          .headers(largeHeaders)

  // TODO(cpovirk): enable when ready (apparently after a change to our GWT emulation)
  public void xtestInitialCapacity_setTwice() {
    MapMaker maker = new MapMaker().initialCapacity(16);
    try {
      // even to the same value is not allowed
      maker.initialCapacity(16);
      fail();
    } catch (IllegalStateException expected) {
    }
  }

  public void testReturnsPlainConcurrentHashMapWhenPossible() {

  private Absent() {}

  @Override
  public boolean isPresent() {
    return false;
  }

  @Override
  public T get() {
    throw new IllegalStateException("Optional.get() cannot be called on an absent value");
  }

  @Override
  public T or(T defaultValue) {
    return checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
  }

  @SuppressWarnings("unchecked") // safe covariant cast