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}.
 *

import java.util.List;
import java.util.NoSuchElementException;
import java.util.PriorityQueue;
import java.util.Queue;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.NonNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * This class contains static utility methods that operate on or return objects of type {@link

import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.stream.Collector;
import java.util.stream.Collectors;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link NavigableMap} whose contents will never change, with many other important properties
 * detailed at {@link ImmutableCollection}.
 *

import java.util.Set;
import java.util.Vector;
import junit.framework.AssertionFailedError;
import junit.framework.Test;
import junit.framework.TestCase;
import junit.framework.TestSuite;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Unit test for {@code Iterators}.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault
public class IteratorsTest extends TestCase {

import java.util.Set;
import java.util.SortedSet;
import java.util.stream.Collector;
import java.util.stream.Stream;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Provides static methods acting on or generating a {@code Multimap}.
 *
 * <p>See the Guava User Guide article on <a href=