putEntries(map, entries);
                    map.putAll(ENTRIES_TO_FILTER);
                    return Maps.filterKeys(map, FILTER_KEYS);
                  }
                })
            .named("Maps.filterKeys[Map, Predicate]")
            .withFeatures(
                MapFeature.ALLOWS_NULL_KEYS,
                MapFeature.ALLOWS_NULL_VALUES,

                    multimap =
                        Multimaps.filterKeys(multimap, Predicates.not(Predicates.equalTo("foo")));
                    return Multimaps.filterKeys(
                        multimap, Predicates.not(Predicates.equalTo("bar")));
                  }
                })
            .named("Multimaps.filterKeys[Multimaps.filterKeys[ListMultimap], Predicate]")
            .withFeatures(

  public void testFilterKeys() {
    Multimap<String, Integer> unfiltered = HashMultimap.create();
    unfiltered.put("foo", 55556);
    unfiltered.put("badkey", 1);
    Multimap<String, Integer> filtered = Multimaps.filterKeys(unfiltered, KEY_PREDICATE);
    assertEquals(1, filtered.size());
    assertTrue(filtered.containsEntry("foo", 55556));
  }

  private static final Predicate<Integer> VALUE_PREDICATE =
      new Predicate<Integer>() {

  public void testFilterKeys() {
    Multimap<String, Integer> unfiltered = HashMultimap.create();
    unfiltered.put("foo", 55556);
    unfiltered.put("badkey", 1);
    Multimap<String, Integer> filtered = Multimaps.filterKeys(unfiltered, KEY_PREDICATE);
    assertEquals(1, filtered.size());
    assertTrue(filtered.containsEntry("foo", 55556));
  }

  private static final Predicate<Integer> VALUE_PREDICATE =
      new Predicate<Integer>() {

  abstract Map<String, Integer> createUnfiltered();

  public void testFilteredKeysIllegalPut() {
    Map<String, Integer> unfiltered = createUnfiltered();
    Map<String, Integer> filtered = Maps.filterKeys(unfiltered, NOT_LENGTH_3);
    filtered.put("a", 1);
    filtered.put("b", 2);
    assertEquals(ImmutableMap.of("a", 1, "b", 2), filtered);

    try {
      filtered.put("yyy", 3);
      fail();

  abstract Map<String, Integer> createUnfiltered();

  public void testFilteredKeysIllegalPut() {
    Map<String, Integer> unfiltered = createUnfiltered();
    Map<String, Integer> filtered = Maps.filterKeys(unfiltered, NOT_LENGTH_3);
    filtered.put("a", 1);
    filtered.put("b", 2);
    assertEquals(ImmutableMap.of("a", 1, "b", 2), filtered);

    try {
      filtered.put("yyy", 3);
      fail();

import com.google.common.base.Predicate;
import java.util.List;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of {@link Multimaps#filterKeys(ListMultimap, Predicate)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class FilteredKeyListMultimap<K extends @Nullable Object, V extends @Nullable Object>

import com.google.common.base.Predicate;
import java.util.List;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of {@link Multimaps#filterKeys(ListMultimap, Predicate)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class FilteredKeyListMultimap<K extends @Nullable Object, V extends @Nullable Object>

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

/**
 * Implementation of {@link Multimaps#filterKeys(SetMultimap, Predicate)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class FilteredKeySetMultimap<K extends @Nullable Object, V extends @Nullable Object>

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#filterKeys(Multimap, Predicate)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
class FilteredKeyMultimap<K extends @Nullable Object, V extends @Nullable Object>