[java] Difference between JSONObject and JSONArray

After having a short look at Google I found this link that describes the difference, yet from a syntax point of view.

When would one be preferred over the other in a programming scenario?

I know, all of the previous answers are insightful to your question. I had too like you this confusion just one minute before finding this SO thread. After reading some of the answers, here is what I get: A JSONObject is a JSON-like object that can be represented as an element in the array, the JSONArray. In other words, a JSONArray can contain a (or many) JSONObject.

The usage of both can be depended on the structure of your data.

Simply, You can use the Nested Objects approach if you plan to give priority to a unique identifier such as a Primary Key.

eg:

  {
     "Employees" : {
           "001" : {
               "Name" : "Alan",
               "Children" : ["Walker", "Dua", "Lipa"]
                },
           "002" : {
               "Name" : "Ezio",
               "Children" : ["Kenvey", "Connor", "Edward"]
                }
      }

Or, Use the Array first approach if you intend to store a set of values with no need to identify uniquely.

eg:

 [
     {
        "Employees":[
               {
                   "Name" : "Alan",
                   "Children" : ["Walker", "Dua", "Lipa"]
               },
               {
                   "Name" : "Ezio",
                   "Children" : ["Kenvey", "Connor", "Edward"]
               }
          ]
       }
   ]

Although you could use the second method with an identifier, it can be harder or too complex to query and understand in some scenarios. Also depending on the database one may have to apply a suitable approach. Eg: MongoDB / Firebase

When a JSON start's with {} it is a ObjectJSON object and when it start's with [] it is an Array JOSN Array

An JSON array can consist of a/many objects and that is called an array of objects

Best programmatically Understanding.

when syntax is {}then this is JsonObject

when syntax is [] then this is JsonArray

A JSONObject is a JSON-like object that can be represented as an element in the JSONArray. JSONArray can contain a (or many) JSONObject

Hope this will helpful to you !

To understand it in a easier way, following are the diffrences between JSON object and JSON array:

Link to Tabular Difference : https://i.stack.imgur.com/GIqI9.png

JSON Array

1. Arrays in JSON are used to organize a collection of related items
   (Which could be JSON objects)
2.  Array values must be of type string, number, object, array, boolean or null
3.  Syntax: 
           [ "Ford", "BMW", "Fiat" ]
4.  JSON arrays are surrounded by square brackets []. 
    **Tip to remember**  :  Here, order of element is important. That means you have 
    to go straight like the shape of the bracket i.e. straight lines. 
   (Note :It is just my logic to remember the shape of both.) 
5.  Order of elements is important. Example:  ["Ford","BMW","Fiat"] is not 
    equal to ["Fiat","BMW","Ford"]
6.  JSON can store nested Arrays that are passed as a value.

JSON Object

1.  JSON objects are written in key/value pairs.
2.  Keys must be strings, and values must be a valid JSON data type (string, number, 
    object, array, boolean or null).Keys and values are separated by a colon.
    Each key/value pair is separated by a comma.
3.  Syntax:
         { "name":"Somya", "age":25, "car":null }
4.  JSON objects are surrounded by curly braces {} 
    Tip to remember : Here, order of element is not important. That means you can go 
    the way you like. Therefore the shape of the braces i.e. wavy. 
    (Note : It is just my logic to remember the shape of both.)
5.  Order of elements is not important. 
    Example:  { rollno: 1, firstname: 'Somya'} 
                   is equal to 
             { firstname: 'Somya', rollno: 1}
6.  JSON can store nested objects in JSON format in addition to nested arrays.

I always use object, it is more easily extendable, JSON array is not. For example you originally had some data as a json array, then you needed to add a status header on it you'd be a bit stuck, unless you'd nested the data in an object. The only disadvantage is a slight increase in complexity of creation / parsing.

So instead of

[datum0, datum1, datumN]

You'd have

{data: [datum0, datum1, datumN]}

then later you can add more...

{status: "foo", data: [datum0, datum1, datumN]}

The difference is the same as a (Hash)Map vs List.

JSONObject:

• Contains named values (key->value pairs, tuples or whatever you want to call them)
  • like {ID : 1}
• Order of elements is not important
  • a JSONObject of {id: 1, name: 'B'} is equal to {name: 'B', id: 1}.

JSONArray:

• Contains only series values
  • like [1, 'value']
• Order of values is important
  • array of [1,'value'] is not the same as ['value',1]

Example

JSON Object --> { "":""}

JSON Array --> [ , , , ]

{"employees":[
    {"firstName":"John", "lastName":"Doe"},
    {"firstName":"Anna", "lastName":"Smith"},
    {"firstName":"Peter", "lastName":"Jones"}
]}