ComoUsarJSONYNoMorirEnElIntento.java

try {
    JSONObject jsonObject = new JSONObject("{\"pop_up\":{\"message\":\"Download a FREE game!\",\"conversion_id\":\"4f9ecd02b23e5a00080000fa\",\"bid\":22,\"links\":[{\"rel\":\"clicks\",\"href\":\"https://www.revmob.com/api/v4/conversions/4f9ecd02b23e5a00080000fa/clicks.json\"}]}}");
    JSONObject popUp = jsonObject.getJSONObject("pop_up");
    JSONArray links = popUp.getJSONArray("links");
    JSONObject firstLink = links.getJSONObject(0);
    String href = firstLink.getString("href");
    System.out.println("::::: PROFIT! "+href);
} catch (JSONException e) {
    e.printStackTrace();
}