assertEvalsToFalse(nasty);

    Predicate<? super Integer> stillNasty = SerializableTester.reserializeAndAssert(nasty);

    assertEvalsToFalse(stillNasty);
  }

  // enum singleton pattern
  private enum TrimStringFunction implements Function<String, String> {
    INSTANCE;

    @Override
    public String apply(String string) {
      return whitespace().trimFrom(string);
    }
  }

   * <p><b>Comparison to {@code java.util.Optional}:</b> this method is equivalent to Java 8's
   * {@code Optional.orElse(null)}.
   */
  public abstract @Nullable T orNull();

  /**
   * Returns an immutable singleton {@link Set} whose only element is the contained instance if it
   * is present; an empty immutable {@link Set} otherwise.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> this method has no equivalent in Java 8's

    return CollectCollectors.toImmutableMultiset(elementFunction, countFunction);
  }

  /**
   * Returns the empty immutable multiset.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  @SuppressWarnings("unchecked") // all supported methods are covariant
  public static <E> ImmutableMultiset<E> of() {
    return (ImmutableMultiset<E>) RegularImmutableMultiset.EMPTY;
  }

  /**

 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.model.validation;

import javax.inject.Inject;
import javax.inject.Named;
import javax.inject.Singleton;

import java.io.File;
import java.util.Arrays;
import java.util.Deque;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

        }
    }

    private static class SingletonHolder {
        private static final SecurityAuditLogger INSTANCE = new SecurityAuditLogger();
    }

    /**
     * Get the singleton instance
     *
     * @return SecurityAuditLogger instance
     */
    public static SecurityAuditLogger getInstance() {
        return SingletonHolder.INSTANCE;
    }

 *
 * <p>Expressing the immutability guarantee directly in the type that user code references is a
 * powerful advantage. Although Java offers certain immutable collection factory methods, such as
 * {@link Collections#singleton(Object)} and <a
 * href="https://docs.oracle.com/javase/9/docs/api/java/util/Set.html#immutable">{@code Set.of}</a>,
 * we recommend using <i>these</i> classes instead for this reason (as well as for consistency).
 *

            return result;
        } catch (Exception e) {
            log.warn("Failed to create fresh context, using singleton", e);
            try {
                // Fallback to singleton with fresh auth
                NtlmPasswordAuthentication auth =
                        new NtlmPasswordAuthentication(SingletonContext.getInstance(), WORKGROUP, USERNAME, PASSWORD);

    // ===================================================================================
    //                                                                           Singleton
    //                                                                           =========
    private static final UserDbm _instance = new UserDbm();

    private UserDbm() {
    }

 *
 * Use `new OkHttpClient()` to create a shared instance with the default settings:
 *
 * ```java
 * // The singleton HTTP client.
 * public final OkHttpClient client = new OkHttpClient();
 * ```
 *
 * Or use `new OkHttpClient.Builder()` to create a shared instance with custom settings:
 *
 * ```java
 * // The singleton HTTP client.
 * public final OkHttpClient client = new OkHttpClient.Builder()

  @SuppressWarnings("unchecked")
  static <T extends @Nullable Object> UnmodifiableListIterator<T> emptyListIterator() {
    return (UnmodifiableListIterator<T>) ArrayItr.EMPTY;
  }

  /**
   * This is an enum singleton rather than an anonymous class so ProGuard can figure out it's only
   * referenced by emptyModifiableIterator().
   */
  private enum EmptyModifiableIterator implements Iterator<Object> {
    INSTANCE;

    @Override