return new TestStringMultisetGenerator() {
      @Override
      protected Multiset<String> create(String[] elements) {
        Multiset<String> multiset1 = LinkedHashMultiset.create();
        Multiset<String> multiset2 = LinkedHashMultiset.create();
        for (int i = 0; i < elements.length; i++) {
          String element = elements[i];
          if (multiset1.contains(element) || multiset2.contains(element)) {

    return new TestStringMultisetGenerator() {
      @Override
      protected Multiset<String> create(String[] elements) {
        Multiset<String> multiset1 = LinkedHashMultiset.create();
        Multiset<String> multiset2 = LinkedHashMultiset.create();
        for (int i = 0; i < elements.length; i++) {
          String element = elements[i];
          if (multiset1.contains(element) || multiset2.contains(element)) {

import static junit.framework.TestCase.fail;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.LinkedHashMultiset;
import com.google.common.collect.Lists;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multiset;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

import static junit.framework.TestCase.fail;

import com.google.common.annotations.GwtCompatible;
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.LinkedHashMultiset;
import com.google.common.collect.Lists;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multiset;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;

        return HashMultiset.create(contents);
      }
    },
    LinkedHashMultisetImpl {
      @Override
      public <E extends Comparable<E>> Multiset<E> create(Collection<E> contents) {
        return LinkedHashMultiset.create(contents);
      }
    },
    ConcurrentHashMultisetImpl {
      @Override
      public <E extends Comparable<E>> Multiset<E> create(Collection<E> contents) {

    }

    {
      ImmutableMultiset.Builder<String> builder = ImmutableMultiset.builder();
    Multiset<@Nullable String> multisetWithNull =
        LinkedHashMultiset.create(Arrays.<@Nullable String>asList("a", null, "b"));
      assertThrows(
          NullPointerException.class, () -> builder.addAll((Multiset<String>) multisetWithNull));
    }
  }

        return HashMultiset.create(contents);
      }
    },
    LinkedHashMultisetImpl {
      @Override
      public <E extends Comparable<E>> Multiset<E> create(Collection<E> contents) {
        return LinkedHashMultiset.create(contents);
      }
    },
    ConcurrentHashMultisetImpl {
      @Override
      public <E extends Comparable<E>> Multiset<E> create(Collection<E> contents) {

    }

    {
      ImmutableSortedMultiset.Builder<String> builder = ImmutableSortedMultiset.naturalOrder();
      Multiset<String> multisetWithNull = LinkedHashMultiset.create(asList("a", null, "b"));
      assertThrows(NullPointerException.class, () -> builder.addAll(multisetWithNull));
    }
  }

  public void testBuilderAddCopiesHandlesNullsCorrectly() {

    }

    {
      ImmutableMultiset.Builder<String> builder = ImmutableMultiset.builder();
    Multiset<@Nullable String> multisetWithNull =
        LinkedHashMultiset.create(Arrays.<@Nullable String>asList("a", null, "b"));
      assertThrows(
          NullPointerException.class, () -> builder.addAll((Multiset<String>) multisetWithNull));
    }
  }