// 3. Exploiting the power of arrays
MongoCollection<Document> collection = client
  .getDatabase("test")
  .getCollection("arrayUpdatesTest");

collection.updateOne(
  Filters.eq("_id", 1),
  Updates.set("a.$[i].b", 2),

new UpdateOptions()
  .arrayFilters(
    Collections.singletonList(
      Filters.eq("i.b", 0))));