Class cast exception [JSONArray cannot be cast to org.json.simple.JSONObject]

If you have a JSONObject and you are trying to convert it to a list, it is not enough to simply cast it to ArrayList as shown here.

ArrayList arrayList = (ArrayList) jsonObject.get(category);

This will throw a ClassCastException.

java.lang.ClassCastException: class org.json.JSONArray cannot be cast to class java.util.ArrayList (org.json.JSONArray is in unnamed module of loader org.springframework.boot.loader.LaunchedURLClassLoader @23ab930d; java.util.ArrayList is in module java.base of loader 'bootstrap')

This is because your JSON contains an array. So create a JSONArray and iterate over it.

JSONArray jsonArray = jsonObject.getJSONArray(category);

ArrayList<Object> arrayList = new ArrayList<Object>();
if (jsonArray != null) {
    for (int i=0; i<jsonArray.length(); i++){
        arrayList.add(jsonArray.get(i));
        System.out.println("Adding to the list {}", jsonArray.get(i));
    }
}