Question

First code:

    Bond[] bonds = null;
    try
    {
        JSONArray jsonArray = new JSONArray(result);
        bonds = new Bond[jsonArray.length()];
        for (int i = 0; i < jsonArray.length(); i++)
        {
            JSONObject json = jsonArray.getJSONObject(i);
            bonds[i] = new Bond(json);
        }
    }
    catch (JSONException e)
    {
        e.printStackTrace();
    }

Second:

    Announcement[] announcements = null;
    try
    {
        JSONArray jsonArray = new JSONArray(result);
        announcements = new Announcement[jsonArray.length()];
        for (int i = 0; i < jsonArray.length(); i++)
        {
            JSONObject json = jsonArray.getJSONObject(i);
            announcements[i] = new Announcement(json);
        }
    }
    catch (JSONException e)
    {
        e.printStackTrace();
    }

I am thinking about extracting a method which will cover these two codes. I think the method should look more or less like this:

static Object[] getObjectsArray(String jsonString, Class<?> cls)
{
    Object[] objects = null;
    try
    {
        JSONArray jsonArray = new JSONArray(jsonString);
        objects = (Object[]) Array.newInstance(cls, jsonArray.length());
        for (int i = 0; i < jsonArray.length(); i++)
        {
            JSONObject json = jsonArray.getJSONObject(i);
            objects[i] = new Announcement(json); // FIXME: How to pass "json" arg to the constructor with cls.newInstance()?
        }
    }
    catch (JSONException e)
    {
        e.printStackTrace();
    }
    return objects;
}

So later instead of first code I can just call Bond[] bonds = (Bond[]) getObjectsArray(jsonArray, Bond).

This is the most problematic line:

objects[i] = new Announcement(json); // FIXME: How to pass "json" arg to the constructor with cls.newInstance()?

Answer 1

You can use the following syntax to use a constructor with arguments (I assume the argument of the constructor is a JSONObject and that the constructor is public – if it is not, use the getDeclaredConstructor method):

Class<Announcement> cls = Announcement.class; //the second argument of your method
objects[i] = cls.getConstructor(JSONObject.class).newInstance(json);