I can\'t figure out how to determine is an element that lives inside a json array is null. To check if the jsonObject itself is null, you simply use:
jsonObj
Try .isNull():
.isNull()
For your example:
if(!mapItem.isNull("date")) { //Value is not null }
However, to answer the title of this question, "how to tell if a JSONArray element is null", use .equals()
.equals()
So, to check if index 1 is null:
if (!jsonArray.get(1).equals(null)) { //jsonArray[1] is not null }