"IllegalStateException: Expected BEGIN_OBJECT but was STRING" error in JSON file

Question

I'm making a project (for a programming class in uni) but when I try to run it in Android Studio, a warning appears very briefly in the emulator:

java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 5 column 21 path $[0].dateOfBirth

This is my JSON file:

{
  "fighters": [
    {
      "id": 1,
      "name": "Karl",
      "dateOfBirth": "20-03-1975",
      "level": 4,
      "image": "karl.png"
    },
    {
      "id": 2,
      "name": "Geralt",
      "dateOfBirth": "16-08-1964",
      "level": 8,
      "image": "Geralt.png"
    },
    {
      "id": 3,
      "name": "Darrak",
      "dateOfBirth": "25-11-1940",
      "level": 5,
      "image": "Darrak.png"
    },
    {
      "id": 4,
      "name": "Jafar",
      "dateOfBirth": "09-02-1920",
      "level": 9,
      "image": "Jafar.png"
    },
    {
      "id": 5,
      "name": "Cornelius",
      "dateOfBirth": "28-06-1988",
      "level": 2,
      "image": "Cornelius.png"
    },
    {
      "id": 6,
      "name": "Laila",
      "dateOfBirth": "18-10-1998",
      "level": 5,
      "image": "Laila.png"
    },
    {
      "id": 7,
      "name": "Marianne",
      "dateOfBirth": "01-03-1975",
      "level": 7,
      "image": "Marianne.png"
    },
    {
      "id": 8,
      "name": "Petro",
      "dateOfBirth": "10-07-1974",
      "level": 10,
      "image": "Petro.png"
    },
    {
      "id": 9,
      "name": "Ordelia",
      "dateOfBirth": "18-05-1985",
      "level": 5,
      "image": "Ordelia.png"
    },
    {
      "id": 10,
      "name": "Lucina",
      "dateOfBirth": "21-09-1992",
      "level": 9,
      "image": "Lucina.png"
    },
    {
      "id": 11,
      "name": "Hugo",
      "dateOfBirth": "16-07-1938",
      "level": 6,
      "image": "Hugo.png"
    },
    {
      "id": 12,
      "name": "Sildar",
      "dateOfBirth": "19-12-1980",
      "level": 3,
      "image": "Sildar.png"
    },
    {
      "id": 13,
      "name": "Zenok",
      "dateOfBirth": "30-10-1999",
      "level": 1,
      "image": "Zenok.png"
    },
    {
      "id": 14,
      "name": "Violet",
      "dateOfBirth": "02-04-2001",
      "level": 8,
      "image": "Violet.png"
    },
    {
      "id": 15,
      "name": "Tamara",
      "dateOfBirth": "13-06-1963",
      "level": 4,
      "image": "Tamara.png"
    }
  ],
  "encounters": [
    {
      "id": 1,
      "fighterId": 1,
      "amount_of_monsters": 4,
      "difficulty": "Medium"
    },
    {
      "id": 2,
      "fighterId": 5,
      "amount_of_monsters": 1,
      "difficulty": "Easy"
    },
    {
      "id": 3,
      "fighterId": 5,
      "amount_of_monsters": 2,
      "difficulty": "Medium"
    },
    {
      "id": 4,
      "fighterId": 7,
      "amount_of_monsters": 1,
      "difficulty": "Hard"
    },
    {
      "id": 5,
      "fighterId": 11,
      "amount_of_monsters": 7,
      "difficulty": "Medium"
    },
    {
      "id": 6,
      "fighterId": 7,
      "amount_of_monsters": 2,
      "difficulty": "Easy"
    },
    {
      "id": 7,
      "fighterId": 14,
      "amount_of_monsters": 10,
      "difficulty": "Extreme"
    },
    {
      "id": 8,
      "fighterId": 13,
      "amount_of_monsters": 4,
      "difficulty": "Medium"
    },
    {
      "id": 9,
      "fighterId": 7,
      "amount_of_monsters": 5,
      "difficulty": "Hard"
    },
    {
      "id": 10,
      "fighterId": 3,
      "amount_of_monsters": 5,
      "difficulty": "Easy"
    }
  ]
}

Line 5 is "name": "Karl",

There's something wrong with my dateOfBirth attribute and I don't know why, because to me the syntax looks correct. I've tried reinstalling the app and rebuilding the project but that didn't work.

This is my first time posting a question on StackOverflow, so apologies if something isn't clear. If anyone is able to help, I would greatly appreciate it.

EDIT (additional info)

I'm using Android Studio 3.6, API 29.

Android Gradle Plugin Version: 3.5.3

Gradle Version: 5.4.1

I use GSON to parse the JSON

JDK 11

This is the function I used for the GSON class:

fun getFighters(): Observable<Array<Fighter>> {
        val observable = Observable.create<Array<Fighter>> { emitter ->
            try {
                var connection = connect("${BASE_URL}/fighters")
                val gson = GsonBuilder().create()
                val fighters = gson.fromJson(
                    InputStreamReader(connection.inputStream),
                    Array<Fighter>::class.java
                )
                for (fighter in fighters) {
                    connection = connect("${BASE_URL}/${fighter.image}")
                    fighter.imageBitmap = BitmapFactory.decodeStream(connection.inputStream)
                }
                emitter.onNext(fighters)
            } catch(e: Exception) {
                emitter.onError(e)
            }
        }
        return observable
    }

The BASE_URL is just a testing url since the assignment we have to do doesn't require to actually deploy the app. The for loop is to show the images of the Fighters in a RecyclerView list, so therefore I used a bitmap. Furthermore, here's the basic Fighter data class:

data class Fighter(
    val id: Number,
    val name: String,
    val dateOfBirth: LocalDate,
    val level: Number,
    val image: String,
    var imageBitmap: Bitmap
)

Answer 1

I think the class that you are using for parsing the JSON should be modified as follows.

data class Fighter(
    val id: Number,
    val name: String,
    val dateOfBirth: String,
    val level: Number,
    val image: String,
    var imageBitmap: Bitmap
)

The dateOfBirth is stored as a String in your JSON and you need to fetch that in that way. If you need to convert the value to a LocalDate object, you can always do that later after parsing the information. I hope that helps!