* ImmutableCollection}, such as {@link ImmutableList}. You can, however, convert an existing
 * iterator to an {@code UnmodifiableIterator} using {@link Iterators#unmodifiableIterator}.
 *
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class UnmodifiableIterator<E extends @Nullable Object> implements Iterator<E> {
  /** Constructor for use by subclasses. */

import com.google.common.collect.testing.SampleElements;
import com.google.common.collect.testing.SampleElements.Strings;
import java.util.List;

/**
 * Create multisets of strings for tests.
 *
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class TestStringMultisetGenerator implements TestMultisetGenerator<String> {
  @Override
  public SampleElements<String> samples() {

import com.google.common.collect.testing.TestCollectionGenerator;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Creates multisets, containing sample elements, to be tested.
 *
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface TestMultisetGenerator<E extends @Nullable Object>
    extends TestCollectionGenerator<E> {
  @Override
  Multiset<E> create(Object... elements);

import com.google.common.collect.testing.AbstractCollectionTester;
import java.util.Queue;
import org.junit.Ignore;

/**
 * Base class for queue collection tests.
 *
 * @author Jared Levy
 */
@GwtCompatible
@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
public class AbstractQueueTester<E> extends AbstractCollectionTester<E> {

import com.google.common.collect.testing.AbstractCollectionTester;
import java.util.Queue;
import org.junit.Ignore;

/**
 * Base class for queue collection tests.
 *
 * @author Jared Levy
 */
@GwtCompatible
@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
public class AbstractQueueTester<E> extends AbstractCollectionTester<E> {

import java.util.Collections;
import java.util.List;

/**
 * An abstract {@code TestMultisetGenerator} for generating multisets containing enum values.
 *
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class TestEnumMultisetGenerator implements TestMultisetGenerator<AnEnum> {
  @Override
  public SampleElements<AnEnum> samples() {

import java.util.Collection;
import java.util.Map;

/**
 * Test {@link Multimap#asMap()} for an unmodifiable multimap with {@link MapInterfaceTest}.
 *
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public class UnmodifiableMultimapAsMapImplementsMapTest
    extends AbstractMultimapAsMapImplementsMapTest {

  public UnmodifiableMultimapAsMapImplementsMapTest() {

import java.util.Collections;
import java.util.List;
import java.util.SortedSet;

/**
 * Create integer sets for testing collections that are sorted by natural ordering.
 *
 * @author Chris Povirk
 * @author Jared Levy
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class TestIntegerSortedSetGenerator extends TestIntegerSetGenerator {
  @Override
  protected abstract SortedSet<Integer> create(Integer[] elements);

      /*
       * We'll call the user callback or collect the values only when all inputs complete,
       * regardless of whether some failed. This lets us avoid calling expensive methods like
       * Future.get() when we don't need to (specifically, for whenAllComplete().call*()), and it
       * lets all futures share the same listener.
       *
       * We store `localFutures` inside the listener because `this.futures` might be nulled out by

import com.google.common.collect.Multiset;
import com.google.common.collect.testing.AbstractCollectionTester;
import org.junit.Ignore;

/**
 * Base class for multiset collection tests.
 *
 * @author Jared Levy
 */
@GwtCompatible
@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
public class AbstractMultisetTester<E> extends AbstractCollectionTester<E> {