private final ProblemEmitter emitter;
    private final InternalProblemReporter internalReporter;
    private final Multimap<Throwable, Problem> problemsForThrowables = Multimaps.synchronizedMultimap(HashMultimap.<Throwable, Problem>create());

    public DefaultProblems(ProblemEmitter emitter, CurrentBuildOperationRef currentBuildOperationRef) {
        this(emitter, null, currentBuildOperationRef);
    }

      Multimap<K, V> multimap, @CheckForNull Object mutex) {
    if (multimap instanceof SynchronizedMultimap || multimap instanceof BaseImmutableMultimap) {
      return multimap;
    }
    return new SynchronizedMultimap<>(multimap, mutex);
  }

  static class SynchronizedMultimap<K extends @Nullable Object, V extends @Nullable Object>
      extends SynchronizedObject implements Multimap<K, V> {

      Multimap<K, V> multimap, @CheckForNull Object mutex) {
    if (multimap instanceof SynchronizedMultimap || multimap instanceof BaseImmutableMultimap) {
      return multimap;
    }
    return new SynchronizedMultimap<>(multimap, mutex);
  }

  static class SynchronizedMultimap<K extends @Nullable Object, V extends @Nullable Object>
      extends SynchronizedObject implements Multimap<K, V> {

   * {@code map} and the instances generated by {@code factory} are. Concurrent read operations will
   * work correctly. To allow concurrent update operations, wrap the multimap with a call to {@link
   * #synchronizedMultimap}.
   *
   * <p>Call this method only when the simpler methods {@link ArrayListMultimap#create()}, {@link
   * HashMultimap#create()}, {@link LinkedHashMultimap#create()}, {@link

   * {@code map} and the instances generated by {@code factory} are. Concurrent read operations will
   * work correctly. To allow concurrent update operations, wrap the multimap with a call to {@link
   * #synchronizedMultimap}.
   *
   * <p>Call this method only when the simpler methods {@link ArrayListMultimap#create()}, {@link
   * HashMultimap#create()}, {@link LinkedHashMultimap#create()}, {@link

  }

  public void testOrderingSynchronized() {
    Multimap<String, Integer> multimap = initializeMultimap5();
    assertOrderingReadOnly(Multimaps.synchronizedMultimap(multimap));
  }

  @J2ktIncompatible
  @GwtIncompatible // SeriazableTester
  public void testSerializationOrdering() {
    Multimap<String, Integer> multimap = initializeMultimap5();

 * underlying map and {@link #createCollection()} method return threadsafe classes. Concurrent read
 * operations will work correctly. To allow concurrent update operations, wrap your multimap with a
 * call to {@link Multimaps#synchronizedMultimap}.
 *
 * <p>For serialization to work, the subclass must specify explicit {@code readObject} and {@code
 * writeObject} methods.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 */
@GwtCompatible

 * underlying map and {@link #createCollection()} method return threadsafe classes. Concurrent read
 * operations will work correctly. To allow concurrent update operations, wrap your multimap with a
 * call to {@link Multimaps#synchronizedMultimap}.
 *
 * <p>For serialization to work, the subclass must specify explicit {@code readObject} and {@code
 * writeObject} methods.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 */
@GwtCompatible