Use .has(String) and .isNull(String)

A conservative usage could be;

    if (record.has("my_object_name") && !record.isNull("my_object_name")) {
        // Do something with object.
      }

In a JSON "object" (aka dictionary), there are two ways to represent absent values: Either have no key/value pair at all, or have a key with the JSON value null.

So you either use .add with a proper value what will get translated to null when you build the JSON, or you don't have the .add call.

Problem is caused by :

currentGames[i].oppEmail = current.getString("OppEmail");

line.

Because currentGames Array is initialized with size 2 but not added any item of type CurrentGame.

Instead of using currentGames[i].oppEmail create a object of CurrentGame class add all values then add it in currentGames Array like:

CurrentGame objCurrentGame=new CurrentGame();
if(current.has("OppEmail")){
  objCurrentGame.oppEmail = current.getString("OppEmail");
}
... same for other fields 
...
//Add objCurrentGame to Array
currentGames[i]=objCurrentGame;

use obj.optJSONArray(name) the response will be null if the name does not exists.

JSONObject obj = new JSONObject(result);
   for(int i=1;i<=14;i++) {

        JSONArray arr = obj.optJSONArray(""+i);
        if(arr != null) {
              extraction(arr, i);
        }
   }

The problem is you're not accessing your JSON object correctly - it's an object that contains a response object which contains a respobj object.

Gson example follows. Note the comment in the code - you need to get the response object then get the respobj from it.

public static void main( String[] args )
{
    String jsonObjRecv =  "{\"response\":{\"respobj\":{\"id\":1,\"number\":\"22\",\"validated\":true}},\"status\":\"ok\",\"errors\":null}";

    JsonElement jelement = new JsonParser().parse(jsonObjRecv);
    JsonObject jobject = jelement.getAsJsonObject();

    // Here is where you're making an error. You need to get the outer
    // 'response' object first, then get 'respobj' from that.
    jobject = jobject.getAsJsonObject("response").getAsJsonObject("respobj");

    String result = jobject.get("number").getAsString();

    System.out.println(result);

}

Output:

22

Edit to add: Note I used getAsString() vs. toString() - if you use the latter you get the raw JSON which will incluse the quotes around the value (e.g. the output would be "22")

You can use get() instead of getString(). This way an Object is returned and JSONObject will guess the right type. Works even for null. Note that there is a difference between Java null and org.json.JSONObject$Null.

CASE 3 does not return "nothing", it throws an Exception. So you have to check for the key to exist (has(key)) and return null instead.

public static Object tryToGet(JSONObject jsonObj, String key) {
    if (jsonObj.has(key))
        return jsonObj.opt(key);
    return null;
}

EDIT

As you commented, you only want a String or null, which leads to optString(key, default) for fetching. See the modified code:

package test;

import org.json.JSONObject;

public class Test {

    public static void main(String[] args) {
        // Does not work
        // JSONObject jsonObj  = {"a":"1","b":null};

        JSONObject jsonObj  = new JSONObject("{\"a\":\"1\",\"b\":null,\"d\":1}");

        printValueAndType(getOrNull(jsonObj, "a")); 
        // >>> 1 -> class java.lang.String

        printValueAndType(getOrNull(jsonObj, "b")); 
        // >>> null -> class org.json.JSONObject$Null

        printValueAndType(getOrNull(jsonObj, "d")); 
        // >>> 1 -> class java.lang.Integer

        printValueAndType(getOrNull(jsonObj, "c")); 
        // >>> null -> null
        // throws org.json.JSONException: JSONObject["c"] not found. without a check
    }

    public static Object getOrNull(JSONObject jsonObj, String key) {
        return jsonObj.optString(key, null);
    }

    public static void printValueAndType(Object obj){
        System.out.println(obj + " -> " + ((obj != null) ? obj.getClass() : null)); 
    }
}