The reason for the error is that your JSON at the top level is an array, not an object. That is covered by GSON throwing "Expected BEGIN_OBJECT but was BEGIN_ARRAY"?.

However, the solution there won't work for your JSON because you have an array of mixed types (an object and an array) rather than an array of a single type of object. For that you're going to have to write a custom deserializer (See The section of the Gson user's guide that covers this) or use Gson's JsonParser class directly and extract the data from the parse tree.

Edit from comments above:

If you're the one creating the JSON, it looks like what you want is an array of BoxSearch objects?

Based on your Java BoxSearch class, you'd need JSON structured like:

[
    {
        "lat1" : 39.737567,
        "lat2" : 32.7801399,
        "long1" : -104.98471790000002,
        "long2" : -96.80045109999998,
        "boxes" : [ 
                    {
                      "lat": {
                          "b": 38.88368709500021,
                          "d": 40.620468491667026
                      },
                      "long": {
                          "b": -105.75306170749764,
                          "d": -104.675854661387
                      }
                    }
                  ]
    }
]

However, the way you have Boxes class defined won't work for that. (Did you mean to have an array of them?). As-is it would need to look like:

class Boxes {
    Box lat;
    @SerializedName("long")
    Box lon;
}

class Box {
   String b;
   String d;
}

Now you have an array containing one type of object (BoxSearch) which you could deserialize with:

Type collectionType = new TypeToken<Collection<BoxSearch>>(){}.getType();
Collection<BoxSearch> boxSearchCollection = gson.fromJson(json, collectionType);

If you really don't need an array of these, get rid of the outer array and simply do:

gson.fromJson(json, BoxSearch.class);

Examples from the API:

 Gson gson = new Gson(); // Or use new GsonBuilder().create();
 MyType target = new MyType();
 String json = gson.toJson(target); // serializes target to Json
 MyType target2 = gson.fromJson(json, MyType.class); // deserializes json into target2

For lists or parameterized types:

 Type listType = new TypeToken<List<String>>() {}.getType();
 List<String> target = new LinkedList<String>();
 target.add("blah");

 Gson gson = new Gson();
 String json = gson.toJson(target, listType);
 List<String> target2 = gson.fromJson(json, listType);

API docs and link for more examples