* thin wrapper around {@link java.util.Collections#emptyMap()}, {@link
 * Collections#singletonMap(Object, Object)} and {@link java.util.LinkedHashMap} for empty,
 * singleton and regular maps respectively. For sorted maps, it's a thin wrapper around {@link
 * java.util.TreeMap}.
 *
 * @see ImmutableSortedMap
 * @author Hayward Chan
 */

   * <p><b>Performance note:</b> the instance returned is a singleton.
   */
  @SuppressWarnings({"unchecked"}) // fully variant implementation (never actually produces any Es)
  public static <E> ImmutableSet<E> of() {
    return (ImmutableSet<E>) RegularImmutableSet.EMPTY;
  }

  /**
   * Returns an immutable set containing the given element. Preferred over {@link

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.collect.testing.Helpers.copyToSet;
import static com.google.common.collect.testing.Helpers.mapEntry;
import static java.util.Collections.singleton;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.Multimap;

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

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

import java.io.File;
import java.io.IOException;
import java.lang.reflect.Method;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;

import eu.maveniverse.domtrip.maven.MavenPomElements;
import org.apache.maven.api.cli.mvnup.UpgradeOptions;
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.cling.invoker.mvnup.UpgradeContext;

import static eu.maveniverse.domtrip.maven.MavenPomElements.Elements.ARTIFACT_ID;
import static eu.maveniverse.domtrip.maven.MavenPomElements.Elements.BUILD;

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

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.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;

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

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

import java.io.File;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;

    return CollectCollectors.toImmutableRangeMap(keyFunction, valueFunction);
  }

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

   * <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

import static com.google.common.truth.Truth.assertThat;
import static java.util.Arrays.asList;
import static java.util.Arrays.sort;
import static java.util.Collections.emptyList;
import static java.util.Collections.singleton;
import static java.util.Collections.sort;
import static java.util.Collections.unmodifiableList;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;