First, list is not a JsonObject it's an array, so you should get it doing:
JSONArray jlist = (JSONArray) jObj.get("list");
Depending of which library you are using the syntax can change but the logic is the same, I'm explaining using json simple lib.
after that you should iterate your list array, something like this:
for (int i = 0; i < jlist.size(); i++){
// get all your objects and your weather array
// to get your weather array the logic is the same:
JSONArray jArrayWeather = (JSONArray) jObj.get("weather");
for (int j = 0; j < jArrayWeather ; j++){
//and here you can get your id, main, description and icon using j index
JSONObject currentObj = (JSONObject) jArrayWeather.get(j);
String main = (String) currentObj.get("main");
}
}
I didn't test this code, so follow the idea and try to do it yourself. Take a look here as we can see you haven't experience with json