History.java

public class History {
    public String date;
    public HistoryElements elements;
}

HistoryElements.java

public class HistoryElements {
    public String volume;
    public String high;
    public String low;
    public String close;
    public String open;
}

Main.java

import java.util.List;

public class Main {

    public static final String jsonString = "{\n" +
            "    \"name\": \"AAPL\",\n" +
            "    \"history\": {\n" +
            "        \"2019-03-05\": {\n" +
            "            \"open\": \"175.94\",\n" +
            "            \"close\": \"175.53\",\n" +
            "            \"high\": \"176.00\",\n" +
            "            \"low\": \"174.54\",\n" +
            "            \"volume\": \"19163899\"\n" +
            "        },\n" +
            "        \"2019-03-04\": {\n" +
            "            \"open\": \"175.69\",\n" +
            "            \"close\": \"175.85\",\n" +
            "            \"high\": \"177.75\",\n" +
            "            \"low\": \"173.97\",\n" +
            "            \"volume\": \"27436203\"\n" +
            "        }\n" +
            "    }\n" +
            "} ";

    public static void main(String[] args) {
        try {
            Repo repo = RepoParser.parseRepo(jsonString);
            System.out.println(repo.name);
        } catch (Exception e) {
            e.printStackTrace();
        }

        return;
    }
}

Repo.java

import java.util.ArrayList;

public class Repo {
    public String name;
    public ArrayList<History> histories;

    public Repo() {
        histories = new ArrayList<History>();
    }
}

RepoParser.java

import com.oracle.javafx.jmx.json.JSONException;
import org.json.JSONObject;

import java.text.ParseException;
import java.util.ArrayList;
import java.util.Iterator;

public class RepoParser {
    public static Repo parseRepo(String jsonString) throws ParseException, JSONException {

        JSONObject jsonObject = new JSONObject(jsonString);
        Iterator<?> iterator = jsonObject.keys();
        Repo repo = new Repo();

        while (iterator.hasNext()) {
            String obj = iterator.next().toString();

            if (obj.equals("name")) repo.name = obj;
            else repo.histories = parseHistory((JSONObject) jsonObject.get(obj));
        }

        return repo;
    }

    public static ArrayList<History> parseHistory(JSONObject jsonObject) throws ParseException, JSONException {
        Iterator<?> iterator = jsonObject.keys();
        ArrayList<History> historyList = new ArrayList<>();

        while (iterator.hasNext()) {
            String obj = iterator.next().toString();
            History history = new History();
            history.date = obj;
            history.elements = parseHistoryElement((JSONObject) jsonObject.get(obj));

            historyList.add(history);
        }

        return historyList;
    }

    public static HistoryElements parseHistoryElement(JSONObject jsonObject) throws ParseException, JSONException {
        Iterator<?> iterator = jsonObject.keys();
        HistoryElements historyElements = new HistoryElements();

        while (iterator.hasNext()) {
            String obj = iterator.next().toString();

            if (obj.equals("open")) historyElements.open = jsonObject.getString("open");
            if (obj.equals("close")) historyElements.close = jsonObject.getString("close");
            if (obj.equals("high")) historyElements.high = jsonObject.getString("high");
            if (obj.equals("low")) historyElements.low = jsonObject.getString("low");
            if (obj.equals("volume")) historyElements.volume = jsonObject.getString("volume");
        }

        return historyElements;
    }
}

As an answer to this question in StackOverflow.