enumConstantCache = new WeakHashMap<>();

  private static <T extends Enum<T>> Map<String, WeakReference<? extends Enum<?>>> populateCache(
      Class<T> enumClass) {
    Map<String, WeakReference<? extends Enum<?>>> result = new HashMap<>();
    for (T enumInstance : EnumSet.allOf(enumClass)) {
      result.put(enumInstance.name(), new WeakReference<Enum<?>>(enumInstance));

          annotationClass.getDeclaringClass(),
          returnType.getComponentType());
    }
  }

  // This is public so that tests for Feature enums we haven't yet imagined
  // can reuse it.
  public static <E extends Enum<?> & Feature<?>> void assertGoodFeatureEnum(
      Class<E> featureEnumClass) {
    Class<?>[] classes = featureEnumClass.getDeclaredClasses();
    for (Class<?> containedClass : classes) {

          annotationClass.getDeclaringClass(),
          returnType.getComponentType());
    }
  }

  // This is public so that tests for Feature enums we haven't yet imagined
  // can reuse it.
  public static <E extends Enum<?> & Feature<?>> void assertGoodFeatureEnum(
      Class<E> featureEnumClass) {
    Class<?>[] classes = featureEnumClass.getDeclaredClasses();
    for (Class<?> containedClass : classes) {

    public Chars() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super('b', 'a', 'c', 'd', 'e');
    }
  }

  public static class Enums extends SampleElements<AnEnum> {
    public Enums() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super(AnEnum.B, AnEnum.A, AnEnum.C, AnEnum.D, AnEnum.E);
    }
  }

    public Chars() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super('b', 'a', 'c', 'd', 'e');
    }
  }

  public static class Enums extends SampleElements<AnEnum> {
    public Enums() {
      // elements aren't sorted, to better test SortedSet iteration ordering
      super(AnEnum.B, AnEnum.A, AnEnum.C, AnEnum.D, AnEnum.E);
    }
  }

     * @throws IllegalAccessRuntimeException if the number of actual and formal parameters differ, if primitive arguments cannot be converted, or if the class is related to enums
     * @see Constructor#newInstance(Object[])
     */
    public static <T> T newInstance(final Constructor<T> constructor, final Object... args)
            throws InstantiationRuntimeException, IllegalAccessRuntimeException {

  }

  static <T extends Enum<T>> Optional<T> getEnumIfPresent(Class<T> enumClass, String value) {
    WeakReference<? extends Enum<?>> ref = Enums.getEnumConstants(enumClass).get(value);
    /*
     * We use `fromNullable` instead of `of` because `WeakReference.get()` has a nullable return
     * type.
     *
     * In practice, we are very unlikely to see `null`: The `WeakReference` to the enum constant

   *
   * @since 16.0
   */
  public static <K0 extends Enum<K0>> MultimapBuilderWithKeys<K0> enumKeys(Class<K0> keyClass) {
    checkNotNull(keyClass);
    return new MultimapBuilderWithKeys<K0>() {
      @SuppressWarnings("unchecked")
      @Override
      <K extends K0, V extends @Nullable Object> Map<K, Collection<V>> createMap() {
        // K must actually be K0, since enums are effectively final

   *
   * @since 16.0
   */
  public static <K0 extends Enum<K0>> MultimapBuilderWithKeys<K0> enumKeys(Class<K0> keyClass) {
    checkNotNull(keyClass);
    return new MultimapBuilderWithKeys<K0>() {
      @SuppressWarnings("unchecked")
      @Override
      <K extends K0, V extends @Nullable Object> Map<K, Collection<V>> createMap() {
        // K must actually be K0, since enums are effectively final

import org.jspecify.annotations.Nullable;

/**
 * Supplies an arbitrary "default" instance for a wide range of types, often useful in testing
 * utilities.
 *
 * <p>Covers arrays, enums and common types defined in {@code java.lang}, {@code java.lang.reflect},
 * {@code java.io}, {@code java.nio}, {@code java.math}, {@code java.util}, {@code