*
 * <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/en/java/javase/25/docs/api/java.base/java/util/Set.html#unmodifiable">{@code
 * Set.of}</a>, we recommend using <i>these</i> classes instead for this reason (as well as for

    return CollectCollectors.toImmutableBiMap(keyFunction, valueFunction);
  }

  /**
   * Returns the empty bimap.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  // Casting to any type is safe because the set will never hold any elements.
  @SuppressWarnings("unchecked")
  public static <K, V> ImmutableBiMap<K, V> of() {

 *
 * <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/en/java/javase/25/docs/api/java.base/java/util/Set.html#unmodifiable">{@code
 * Set.of}</a>, we recommend using <i>these</i> classes instead for this reason (as well as for

import org.apache.maven.api.cli.mvnup.UpgradeOptions;
import org.apache.maven.api.di.Inject;
import org.apache.maven.api.di.Named;
import org.apache.maven.api.di.Priority;
import org.apache.maven.api.di.Singleton;
import org.apache.maven.api.model.Build;
import org.apache.maven.api.model.Model;
import org.apache.maven.api.model.Parent;
import org.apache.maven.api.model.Plugin;
import org.apache.maven.api.model.PluginManagement;

    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;
  }

  /**

    return CollectCollectors.flatteningToImmutableListMultimap(keyFunction, valuesFunction);
  }

  /**
   * Returns the empty multimap.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  // Casting is safe because the multimap will never hold any elements.
  @SuppressWarnings("unchecked")
  public static <K, V> ImmutableListMultimap<K, V> of() {

    return CollectCollectors.toImmutableRangeSet();
  }

  /**
   * Returns an empty immutable range set.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  @SuppressWarnings("unchecked")
  public static <C extends Comparable> ImmutableRangeSet<C> of() {
    return (ImmutableRangeSet<C>) EMPTY;
  }

  /**

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

    private UserDbm() {
    }

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

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

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;

@GwtCompatible
public abstract class ImmutableMultimap<K, V> extends BaseImmutableMultimap<K, V>
    implements Serializable {

  /**
   * Returns an empty multimap.
   *
   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  public static <K, V> ImmutableMultimap<K, V> of() {
    return ImmutableListMultimap.of();
  }

  /** Returns an immutable multimap containing a single entry. */