Parsing Android JSON Object within JSON Object into an arry

Question

I'm currently receiving a JSON response from a server that I'm attempting to parse. Getting the actual properties has been simple, but I'm having trouble parsing an object within the response into an array that I can then parse into a table for display.

{
    "response": "User exists",
    "data": {
        "id": 5,
        "list": 7,
        "first_name": "Aaron",
        "last_name": "Test",
        "email": "testing@testdomaij.com",
        "custom_fields": {
            "Is this a question?": "This is an answer",
            "Test Question": "Test answer!"
        },
        "created_at": "Oct 14, 2015"
    }
}

I'm already passing the data object into a POJO and am able to get all of the strings and integers, but I'm not sure how to parse the custom_fields object into an array. The keys and values will be different for every user, and I need to find a way to display them.

My current User object that parses the data is as follows:

import android.os.Parcel;
import android.os.Parcelable;

import com.google.gson.annotations.SerializedName;

public class User implements Parcelable {

    private String id;
    private String list;
    @SerializedName("first_name")
    private String firstName;
    @SerializedName("last_name")
    private String lastName;
    private String email;
    @SerializedName("custom_fields")
    private CustomFields customFields;
    @SerializedName("created_at")
    private String createdAt;

    public User() {

    }

    public User(Parcel source) {
        id = source.readString();
        list = source.readString();
        firstName = source.readString();
        lastName = source.readString();
        email = source.readString();
        createdAt = source.readString();
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getList() {
        return list;
    }

    public void setList(String list) {
        this.list = list;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public void getCustomFields() {
       // I have no idea how to parse and return as an array
    }

    public String getCreatedAt() {
        return createdAt;
    }

    public void setCreatedAt(String createdAt) {
        this.createdAt = createdAt;
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(id);
        dest.writeString(list);
        dest.writeString(firstName);
        dest.writeString(lastName);
        dest.writeString(email);
        dest.writeString(createdAt);
    }

    public static Creator<User> CREATOR = new Creator<User>() {

        @Override
        public User createFromParcel(Parcel source) {
            return new User(source);
        }

        @Override
        public User[] newArray(int size) {
            return new User[size];
        }

    };
}

How do I go about parsing the keys and values of the custom_fields object and returning them as an array I can use?