我正在使用java和mongodb从文档中检索结果。我想从imdb.rating获取一个数值，但似乎找不到解决方案。我可以将其作为字符串获取，然后解析该值，但它也会包含“$numberdouble”部分，这会给我带来问题。
文档片段：

{
  "_id": {
    "$oid": "573a1390f29313caabcd42e8"
  },
  "plot": "A group of bandits stage a brazen train hold-up, only to find a determined posse hot on their heels.",
  "genres": [
    "Short",
    "Western"
  ],
  "runtime": 11,
  "cast": [
    "A.C. Abadie",
    "Gilbert M. 'Broncho Billy' Anderson",
    "George Barnes",
    "Justus D. Barnes"
  ],
  "poster": "https://m.media-amazon.com/images/M/MV5BMTU3NjE5NzYtYTYyNS00MDVmLWIwYjgtMmYwYWIxZDYyNzU2XkEyXkFqcGdeQXVyNzQzNzQxNzI@._V1_SY1000_SX677_AL_.jpg",
  "title": "The Great Train Robbery",
  "fullplot": "Among the earliest existing films in American cinema - notable as the first film that presented a narrative story to tell - it depicts a group of cowboy outlaws who hold up a train and rob the passengers. They are then pursued by a Sheriff's posse. Several scenes have color included - all hand tinted.",
  "languages": [
    "English"
  ],
  "released": {
    "$date": "1903-12-01T00:00:00.000Z"
  },
  "directors": [
    "Edwin S. Porter"
  ],
  "rated": "TV-G",
  "awards": {
    "wins": 1,
    "nominations": 0,
    "text": "1 win."
  },
  "lastupdated": "2015-08-13 00:27:59.177000000",
  "year": 1903,
  "imdb": {
    "rating": {
      "$numberDouble": "7.4"
    },
    "votes": 9847,
    "id": 439
  },
  "countries": [
    "USA"
  ],
  "type": "movie",
  "tomatoes": {
    "viewer": {
      "rating": {
        "$numberDouble": "3.7"
      },
      "numReviews": 2559,
      "meter": 75
    },
    "fresh": 6,
    "critic": {
      "rating": {
        "$numberDouble": "7.6"
      },
      "numReviews": 6,
      "meter": 100
    },
    "rotten": 0,
    "lastUpdated": {
      "$date": "2015-08-08T19:16:10.000Z"
    }
  }
}