How to convert Dynamic nested JSON to JAVA Object in android with GSON?

Firstly I guess your example "key7": "something" should actually be "key8..".

Gson can parse any valid JSON to a LinkedTreeMap that you can then loop any way you want. However, your response seems to be static to some extent so you can create a DTO to make accessing values a bit easier. This DTO could be like:

@Getter
public class ResponseWrapper {
    @Getter
    public static class Response {
        private Integer status;
        private Map<Integer, Map<String, Object>> result;       
    }
    private Response response;
}

With this kind of a DTO you could then do foo example (and assuming no Java8 & Streams):

Response rw = new Gson().fromJson(RESPONSE_JSON, ResponseWrapper.class).getResponse();
Set<Entry<Integer, Map<String, Object>>> entries = rw.getResult().entrySet();
for(Entry<Integer, Map<String, Object>> e : entries) {
    Object o = e.getValue().get("key1");
    // do somethigs
}

If your example's result keys (17,18,19) contain a fixed set of keys - so just from key1 to key9 with the same data types - you could create a separate DTO for that also, like:

@Getter
public class ResultItem {
    private Long key1;
    private Long key2;
    private String key3;
    private String key4;
    private String key5;
    private Long key6;
    private Date key7;
    private String key8;
    private String key9;
}

and then your access to values might be just a bit more type safe, for example:

for(Entry<Integer, ResultItem> e : entries) {
    Long longKey1 = e.getValue().getKey1();
    // do somethings
}

at the begging you can need to create your POJO's ,this site to create your POJO JsonToPojoLink

then you can use GSON like this:

   Gson gson = new Gson();
    ResponsePOJO responsePOJO;
    responsePOJO= gson.fromJson(response.toString(),ResponsePOJO.class);

You have a response of result object with multiple object values.
So, you can simply apply a logic behind like,

JSONObject responseCode = response.getJSONObject("response");  
JSONObject resultCode = responseCode.getJSONObject("result");

    if(resultCode.length >0){
        for(int i=0;i<resultCode;i++){
            JSONObject listCode = resultCode.getJSONObject(i);
            String keyVal_1=listCode.getString("key1");
//store keyVal_1 in your arrayList and other keys 
//it will work till the dynamically generated last object you store.
        }
    }