* iterators that don't support {@code remove()}, but all other methods are supported by the map
   * and its views. When given a key that doesn't satisfy the predicate, the map's {@code put()} and
   * {@code putAll()} methods throw an {@link IllegalArgumentException}.
   *
   * <p>When methods such as {@code removeAll()} and {@code clear()} are called on the filtered map

 *   {@literal @Override} public int hashCode() {...}
 *   ...
 * }
 * </pre>
 *
 * <p>No cascading checks are performed against the return values of methods unless the method is a
 * static factory method. Neither are semantics of mutation methods such as {@code
 * someList.add(obj)} checked. For more detailed discussion of supported and unsupported cases, see
 * {@link #testEquals}, {@link #testNulls} and {@link #testSerializable}.

    return (requestCount == 0) ? 1.0 : (double) hitCount / requestCount;
  }

  /**
   * Returns the number of times {@link Cache} lookup methods have returned an uncached (newly
   * loaded) value, or null. Multiple concurrent calls to {@link Cache} lookup methods on an absent
   * value can result in multiple misses, all returning the results of a single cache load
   * operation.
   */
  public long missCount() {

  /**
   * Verifies that a collection is immutable.
   *
   * <p>A collection is considered immutable if:
   *
   * <ol>
   *   <li>All its mutation methods result in UnsupportedOperationException, and do not change the
   *       underlying contents.
   *   <li>All methods that return objects that can indirectly mutate the collection throw
   *       UnsupportedOperationException when those mutators are called.
   * </ol>
   *

    return (requestCount == 0) ? 1.0 : (double) hitCount / requestCount;
  }

  /**
   * Returns the number of times {@link Cache} lookup methods have returned an uncached (newly
   * loaded) value, or null. Multiple concurrent calls to {@link Cache} lookup methods on an absent
   * value can result in multiple misses, all returning the results of a single cache load
   * operation.
   */
  public long missCount() {

import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * An object with an operational state, plus asynchronous {@link #startAsync()} and {@link
 * #stopAsync()} lifecycle methods to transition between states. Example services include
 * webservers, RPC servers and timers.
 *
 * <p>The normal lifecycle of a service is:
 *
 * <ul>
 *   <li>{@linkplain State#NEW NEW} -&gt;

  private static Set<MethodSignature> getPublicStaticMethodsBetween(
      Class<?> descendant, Class<?> ancestor) {
    Set<MethodSignature> methods = newHashSet();
    for (Class<?> clazz : getClassesBetween(descendant, ancestor)) {
      methods.addAll(getPublicStaticMethods(clazz));
    }
    return methods;
  }

  private static Set<MethodSignature> getPublicStaticMethods(Class<?> clazz) {

  private static Set<MethodSignature> getPublicStaticMethodsBetween(
      Class<?> descendant, Class<?> ancestor) {
    Set<MethodSignature> methods = newHashSet();
    for (Class<?> clazz : getClassesBetween(descendant, ancestor)) {
      methods.addAll(getPublicStaticMethods(clazz));
    }
    return methods;
  }

  private static Set<MethodSignature> getPublicStaticMethods(Class<?> clazz) {

/// note | "技术细节"

表单数据的「媒体类型」编码一般为 `application/x-www-form-urlencoded`。

但包含文件的表单编码为 `multipart/form-data`。文件处理详见下节。

编码和表单字段详见 <a href="https://developer.mozilla.org/zh-CN/docs/Web/HTTP/Methods/POST" class="external-link" target="_blank"><abbr title="Mozilla Developer Network">MDN</abbr> Web 文档的 <code>POST</code></a>小节。

///

/// warning | "警告"

   *
   * TODO(cpovirk): Could this be simplified if we modified implementations of LegacyConverter to
   * override methods (probably called "unsafeDoForward" and "unsafeDoBackward") with the same
   * signatures as the methods below, rather than overriding the same doForward and doBackward
   * methods as implementations of normal converters do?
   *