{
      Collector<Cell<String, String, Integer>, ?, ImmutableTable<String, String, Integer>>
          collector = toImmutableTable(Cell::getRowKey, Cell::getColumnKey, t -> null);
      assertThrows(
          NullPointerException.class,
          () -> Stream.of(immutableCell("one", "uno", 1)).collect(collector));
    }
    {

    Collector<Entry<AnEnum, Integer>, ?, ImmutableMap<AnEnum, Integer>> collector =
        toImmutableEnumMap(Entry::getKey, Entry::getValue);
    assertThrows(
        IllegalArgumentException.class,
        () -> Stream.of(mapEntry(AnEnum.A, 1), mapEntry(AnEnum.A, 11)).collect(collector));
  }

  public void testToImmutableMapMerging() {

   * operation is performed. (This differs from the {@code Collector} returned by {@link
   * Collectors#toMap(Function, Function)}, which throws an {@code IllegalStateException}.)
   *
   * @since 33.2.0 (available since 21.0 in guava-jre)
   */
  @IgnoreJRERequirement // Users will use this only if they're already using streams.
  public static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(

    assertNotSame(sortedSet, copy);
  }

  public void testToImmutableSet() {
    Collector<String, ?, ImmutableSet<String>> collector = toImmutableSet();
    Equivalence<ImmutableSet<String>> equivalence =
        Equivalence.equals().onResultOf(ImmutableSet::asList);
    CollectorTester.of(collector, equivalence)
        .expectCollects(ImmutableSet.of("a", "b", "c", "d"), "a", "b", "a", "c", "b", "b", "d");
  }

            .put("two", 2)
            .build();
    CollectorTester.of(collector, equivalence)
        .expectCollects(expected, mapEntry("one", 1), mapEntry("two", 2), mapEntry("three", 3));
  }

  public void testToImmutableSortedMap_exceptionOnDuplicateKey() {
    Collector<Entry<String, Integer>, ?, ImmutableSortedMap<String, Integer>> collector =
        toImmutableSortedMap(Ordering.natural(), Entry::getKey, Entry::getValue);

    checkArgument(fpp < 1.0, "False positive probability (%s) must be < 1.0", fpp);
    return Collector.of(
        () -> BloomFilter.create(funnel, expectedInsertions, fpp),
        BloomFilter::put,
        (bf1, bf2) -> {
          bf1.putAll(bf2);
          return bf1;
        },
        Collector.Characteristics.UNORDERED,
        Collector.Characteristics.CONCURRENT);
  }

  /**

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.stream.Collector;
import jsinterop.annotations.JsMethod;
import org.jspecify.annotations.Nullable;

/**
 * GWT emulated version of {@link com.google.common.collect.ImmutableSet}. For the unsorted sets,

  public static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableMap<K, V>> toImmutableMap(
          Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction) {
    return CollectCollectors.toImmutableMap(keyFunction, valueFunction);
  }

  public static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableMap<K, V>> toImmutableMap(

    CollectorTester.of(collector, equivalence)
        .expectCollects(
            ImmutableMultiset.<TypeWithDuplicates>builder().add(a).addCopies(b1, 2).add(c).build(),
            a,
            b1,
            c,
            b2);
    collector = toImmutableMultiset(e -> e, e -> 1);
    CollectorTester.of(collector, equivalence)
        .expectCollects(

        NullPointerException.class,
        () -> ImmutableSetMultimap.copyOf((Multimap<String, Integer>) input));
  }

  public void testToImmutableSetMultimap() {
    Collector<Entry<String, Integer>, ?, ImmutableSetMultimap<String, Integer>> collector =
        toImmutableSetMultimap(Entry::getKey, Entry::getValue);
    BiPredicate<ImmutableSetMultimap<?, ?>, ImmutableSetMultimap<?, ?>> equivalence =
        Equivalence.equals()