private static boolean isPermutation(List<?> first, List<?> second) {
    if (first.size() != second.size()) {
      return false;
    }
    Multiset<?> firstMultiset = HashMultiset.create(first);
    Multiset<?> secondMultiset = HashMultiset.create(second);
    return firstMultiset.equals(secondMultiset);
  }

  }

  enum MultisetImpl implements CollectionsImplEnum {
    HashMultisetImpl {
      @Override
      public <E extends Comparable<E>> Multiset<E> create(Collection<E> contents) {
        return HashMultiset.create(contents);
      }
    },
    LinkedHashMultisetImpl {
      @Override
      public <E extends Comparable<E>> Multiset<E> create(Collection<E> contents) {

  }

  enum MultisetImpl implements CollectionsImplEnum {
    HashMultisetImpl {
      @Override
      public <E extends Comparable<E>> Multiset<E> create(Collection<E> contents) {
        return HashMultiset.create(contents);
      }
    },
    LinkedHashMultisetImpl {
      @Override
      public <E extends Comparable<E>> Multiset<E> create(Collection<E> contents) {

import static com.google.common.collect.Lists.charactersOf;
import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.assertThrows;

import com.google.common.collect.HashMultiset;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.Iterables;
import com.google.common.collect.Multiset;

        return OldConcurrentHashMultiset.create();
      }
    },
    SYNCHRONIZED_MULTISET() {
      @Override
      Multiset<Integer> get() {
        return Synchronized.multiset(HashMultiset.<Integer>create(), null);
      }
    },
    ;

    abstract Multiset<Integer> get();
  }

  /**
   * Duplication of the old version of ConcurrentHashMultiset (with some unused stuff removed, like

      }
      assertThat(queue).isEmpty();
    }
  }

  public void testRandomAddsAndRemoves() {
    Random random = new Random(0);
    Multiset<Integer> elements = HashMultiset.create();
    MinMaxPriorityQueue<Integer> queue = MinMaxPriorityQueue.create();
    int range = 10_000; // range should be small enough that equal elements occur semi-frequently

        return OldConcurrentHashMultiset.create();
      }
    },
    SYNCHRONIZED_MULTISET() {
      @Override
      Multiset<Integer> get() {
        return Synchronized.multiset(HashMultiset.<Integer>create(), null);
      }
    },
    ;

    abstract Multiset<Integer> get();
  }

  /**
   * Duplication of the old version of ConcurrentHashMultiset (with some unused stuff removed, like

 * multiset. Undefined behavior and bugs will result.
 *
 * <h3>Implementations</h3>
 *
 * <ul>
 *   <li>{@link ImmutableMultiset}
 *   <li>{@link ImmutableSortedMultiset}
 *   <li>{@link HashMultiset}
 *   <li>{@link LinkedHashMultiset}
 *   <li>{@link TreeMultiset}
 *   <li>{@link EnumMultiset}
 *   <li>{@link ConcurrentHashMultiset}
 * </ul>
 *

import static com.google.common.collect.Lists.charactersOf;
import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.assertThrows;

import com.google.common.collect.HashMultiset;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMultimap;
import com.google.common.collect.Iterables;
import com.google.common.collect.Multiset;