Collection<V> values = multimap.get(key); // Needn't be in synchronized block
    synchronized (multimap) { // Synchronizing on multimap, not values!
      Iterator<V> i = values.iterator(); // Must be in synchronized block
      while (i.hasNext()) {
        foo(i.next());
      }
    }
  }

  private static void foo(Object unused) {}

    Collection<V> values = multimap.get(key); // Needn't be in synchronized block
    synchronized (multimap) { // Synchronizing on multimap, not values!
      Iterator<V> i = values.iterator(); // Must be in synchronized block
      while (i.hasNext()) {
        foo(i.next());
      }
    }
  }

  private static void foo(Object unused) {}