JSON parsing with Gson/Moshi in Android Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Gson instance for JSON parsing.

Android Kotlin

val gson = GsonBuilder().[1]().create()

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AserializeNulls

BtoJson

CfromJson

DsetPrettyPrinting

Attempts:

3 left

💡 Hint

Common Mistakes

Using toJson or fromJson here causes errors because they are Gson methods, not GsonBuilder.

The setPrettyPrinting() method enables formatted JSON output when using Gson.

2fill in blank

medium

Complete the code to parse a JSON string into a Kotlin data class using Gson.

Android Kotlin

val user: User = gson.[1](jsonString, User::class.java)

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AparseJson

Bserialize

CfromJson

DtoJson

Attempts:

3 left

💡 Hint

Common Mistakes

Using toJson tries to convert an object to JSON, not parse JSON.

The fromJson() method converts a JSON string into an object of the specified class.

3fill in blank

hard

Fix the error in this Moshi adapter creation code by filling the blank.

Android Kotlin

val moshi = Moshi.Builder().build()
val adapter = moshi.adapter([1]::class.java)

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AUser

BString

Cuser

DJsonAdapter

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name instead of a class causes compile errors.

The adapter method needs the class type, so User::class.java is correct. Using lowercase user is a variable, not a class.

4fill in blank

hard

Fill both blanks to parse a JSON array string into a list of User objects using Gson.

Android Kotlin

val listType = object : TypeToken<[1]<[2]>>() {}.type
val users: List<User> = gson.fromJson(jsonArrayString, listType)

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AList

BUser

CArray

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using Array instead of List causes type mismatch errors.

To parse a JSON array, we use List of User as the type token.

5fill in blank

hard

Fill all three blanks to create a Moshi adapter for a list of User objects and parse JSON.

Android Kotlin

val moshi = Moshi.Builder().build()
val type = Types.newParameterizedType([1]::class.java, [2]::class.java)
val adapter = moshi.adapter<List<[3]>>(type)
val users = adapter.fromJson(jsonArrayString)

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AList

BUser

CArray

DString

Attempts:

3 left

💡 Hint

Common Mistakes

Using Array instead of List or mismatching types causes runtime errors.

We use List as the parameterized type, and User as the class inside the list for Moshi parsing.