@IgnoreJRERequirement
  public java.util.Optional<T> toJavaUtil() {
    return java.util.Optional.ofNullable(orNull());
  }

  Optional() {}

  /**
   * Returns {@code true} if this holder contains a (non-null) instance.
   *
   * <p><b>Comparison to {@code java.util.Optional}:</b> no differences.
   */
  public abstract boolean isPresent();

  /**

import java.lang.reflect.Method;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.EnumSet;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentSkipListSet;

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.Currency;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NavigableMap;

import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ConcurrentLinkedDeque;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.PriorityBlockingQueue;
import junit.framework.Test;
import junit.framework.TestSuite;

/**

 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect.testing;

import com.google.common.annotations.GwtCompatible;
import java.util.List;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Creates sets, containing sample elements, to be tested.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible

import static org.junit.Assert.assertThrows;

import com.google.common.util.concurrent.ClosingFuture.ClosingCallable;
import com.google.common.util.concurrent.ClosingFuture.DeferredCloser;
import com.google.common.util.concurrent.ClosingFuture.ValueAndCloser;
import com.google.common.util.concurrent.ClosingFuture.ValueAndCloserConsumer;
import java.io.Closeable;
import java.util.concurrent.CountDownLatch;

 */

package com.google.common.util.concurrent;

import static com.google.common.util.concurrent.Service.State.FAILED;
import static com.google.common.util.concurrent.Service.State.NEW;
import static com.google.common.util.concurrent.Service.State.RUNNING;
import static com.google.common.util.concurrent.Service.State.STARTING;
import static com.google.common.util.concurrent.Service.State.STOPPING;

 */
package org.apache.maven.api.cli.logging;

import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.maven.api.cli.Logger;

import static java.util.Objects.requireNonNull;

/**
 * Early CLI {@link Logger} that simply accumulates log entries until some point a real logger can emit them. This

 */

package com.google.common.util.concurrent.testing;

import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static org.junit.Assert.assertThrows;

import com.google.common.collect.ImmutableList;
import com.google.common.util.concurrent.ListeningScheduledExecutorService;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;

 */

package com.google.common.util.concurrent.testing;

import static java.util.concurrent.TimeUnit.MILLISECONDS;
import static org.junit.Assert.assertThrows;

import com.google.common.collect.ImmutableList;
import com.google.common.util.concurrent.ListeningScheduledExecutorService;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.CancellationException;