import java.util.concurrent.CopyOnWriteArraySet;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Static utility methods pertaining to {@link Set} instances. Also see this class's counterparts
 * {@link Lists}, {@link Maps} and {@link Queues}.
 *

The Eclipse Public License is available at
  https://www.eclipse.org/legal/epl-2.0/
and the Eclipse Distribution License is available at
  http://www.eclipse.org/org/documents/edl-v10.php.

For an explanation of what dual-licensing means to you, see:
https://www.eclipse.org/legal/eplfaq.php#DUALLIC

****
The epl-2.0 is copied below in order to pass the pkg.go.dev license check (https://pkg.go.dev/license-policy).
****

import com.google.common.testing.NullPointerTester;
import java.util.Collections;
import java.util.List;
import java.util.Set;
import junit.framework.TestCase;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Unit test for {@link Optional}.
 *
 * @author Kurt Alfred Kluever
 */
@ElementTypesAreNonnullByDefault
@GwtCompatible(emulated = true)
public final class OptionalTest extends TestCase {

import com.google.common.collect.testing.features.MapFeature;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map.Entry;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.junit.Ignore;

/**
 * Tester for {@link Multimap#put}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible

import java.lang.reflect.Method;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.List;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.junit.Ignore;

/**
 * A generic JUnit test which tests addAll operations on a collection. Can't be invoked directly;
 * please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.

import com.google.common.collect.Lists;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.ArrayList;
import java.util.List;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tester for equals() and hashCode() methods of a class.
 *
 * <p>The simplest use case is:
 *
 * <pre>
 * new EqualsTester().addEqualityGroup(foo).testEquals();
 * </pre>
 *

import com.google.common.collect.testing.features.MapFeature;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map.Entry;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.junit.Ignore;

/**
 * Tester for {@link Multimap#put}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible

import java.util.Comparator;
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@code SetMultimap} whose set of values for a given key are kept sorted; that is, they comprise
 * a {@link SortedSet}. It cannot hold duplicate key-value pairs; adding a key-value pair that's

import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Tests for {@link Maps#transformValues} when the backing map's views have iterators that don't
 * support {@code remove()}.
 *
 * @author Jared Levy
 */
@GwtCompatible

import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of {@link Multimaps#filterEntries(Multimap, Predicate)}.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault