How to properly convert HashMap<String,List> to Json with array of json object

I have a stream of Kafka messages and wanted to build a HashMap<String,List<Object>> to be used as API response in Json format.

for (ConsumerRecord<String,String> consumerRecord : records) {
    if(!responses.containsKey(consumerRecord.topic())){
        responses.put(consumerRecord.topic(), new ArrayList<Object>());
    }
    responses.get(consumerRecord.topic()).add(JSONObject.stringToValue(consumerRecord.value()));
}

expected response:

{
    "topic1": [
        {"field1":"value1","field2":"value2","field3":"value3"}
    ],
    "topic2": [
        {"field1":"value1","field2":"value2","field3":"value3"},
        {"anotherfield1":"anothervalue1","anotherfield2":"anothervalue2"}
    ]
}

actual response:

{
    "topic1": [
        "{"field1":"value1","field2":"value2","field3":"value3"}"
    ],
    "topic2": [
        "{"field1":"value1","field2":"value2","field3":"value3"}",
        "{"anotherfield1":"anothervalue1","anotherfield2":"anothervalue2"}"
    ]
}

Answer

It is now working using these changes:

HashMap<String,List<Object>> responses = new HashMap<String,List<Object>>();

for (ConsumerRecord<String,String> consumerRecord : records) {
    if(!responses.containsKey(consumerRecord.topic())){
        responses.put(consumerRecord.topic(), new ArrayList<Object>());
    }
    responses.get(consumerRecord.topic()).add(new JSONObject(consumerRecord.value()));
}

jsonObject = new JSONObject(responses);
return jsonObject.toMap();

1. Convert Kafka message string to JSONObject new JSONObject(consumerRecord.value())
2. Construct a JSONObject from a Map using jsonObject = new JSONObject(responses);
3. Return Map<String, Object> using jsonObject.toMap();