How to Write/create a JSON array using Java?

A JSON array is an ordered collection of values that are enclosed in square brackets i.e., it begins with '[' and ends with ']'. The values in the arrays are separated by ',' (comma).

Sample JSON array

{
   "books": [ Java, JavaFX, Hbase, Cassandra, WebGL, JOGL]
}

The JSON-simple is a light weight library which is used to process JSON objects. Using this you can read or, write the contents of a JSON document using Java program.

JSON-Simple maven dependency

Following is the maven dependency for the JSON-simple library ?

<dependencies>
   <dependency>
      <groupId>com.googlecode.json-simple</groupId>
      <artifactId>json-simple</artifactId>
      <version>1.1.1</version>
   </dependency>
</dependencies>

Paste this with in the <dependencies> </dependencies> tag at the end of your pom.xml file. (before </project> tag)

Example

To create an array in a JSON file using a Java program ?

• Instantiate the JSONObject class of the json-simple library.

//Creating a JSONObject object
JSONObject jsonObject = new JSONObject();

• Insert the required key-value pairs using the put() method of the JSONObject class.

jsonObject.put("key", "value");

• Create a JSON array by instantiating the JSONArray class and add, elements to the created array using the add() method of the JSONArray class.

JSONArray array = new JSONArray();
array.add("element_1");
array.add("element_2");
array.add("element_3");

• After adding all the required elements add the array into the JSON document using the put() method as ?

jsonObject.put("contact",array);

• Write the created JSON object into a file using the FileWriter class as ?

FileWriter file = new FileWriter("E:/json_array_output.json");
file.write(jsonObject.toJSONString());
file.close();

Following Java program creates a JSON object with an array in it and writes it into a file named json_array_output.json.

Example

<span class="kwd">import</span><span class="pln"> java</span><span class="pun">.</span><span class="pln">io</span><span class="pun">.</span><span class="typ">FileWriter</span><span class="pun">;</span><span class="pln">
</span><span class="kwd">import</span><span class="pln"> java</span><span class="pun">.</span><span class="pln">io</span><span class="pun">.</span><span class="typ">IOException</span><span class="pun">;</span><span class="pln">
</span><span class="kwd">import</span><span class="pln"> org</span><span class="pun">.</span><span class="pln">json</span><span class="pun">.</span><span class="pln">simple</span><span class="pun">.</span><span class="typ">JSONArray</span><span class="pun">;</span><span class="pln">
</span><span class="kwd">import</span><span class="pln"> org</span><span class="pun">.</span><span class="pln">json</span><span class="pun">.</span><span class="pln">simple</span><span class="pun">.</span><span class="typ">JSONObject</span><span class="pun">;</span><span class="pln">
</span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">class</span><span class="pln"> </span><span class="typ">WritingJSONArray</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
   </span><span class="kwd">public</span><span class="pln"> </span><span class="kwd">static</span><span class="pln"> </span><span class="kwd">void</span><span class="pln"> main</span><span class="pun">(</span><span class="typ">String</span><span class="pln"> args</span><span class="pun">[])</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
      </span><span class="com">//Creating a JSONObject object</span><span class="pln">
      </span><span class="typ">JSONObject</span><span class="pln"> jsonObject </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">JSONObject</span><span class="pun">();</span><span class="pln">
      </span><span class="com">//Inserting key-value pairs into the json object</span><span class="pln">
      jsonObject</span><span class="pun">.</span><span class="pln">put</span><span class="pun">(</span><span class="str">"ID"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"1"</span><span class="pun">);</span><span class="pln">
      jsonObject</span><span class="pun">.</span><span class="pln">put</span><span class="pun">(</span><span class="str">"First_Name"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"Krishna Kasyap"</span><span class="pun">);</span><span class="pln">
      jsonObject</span><span class="pun">.</span><span class="pln">put</span><span class="pun">(</span><span class="str">"Last_Name"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"Bhagavatula"</span><span class="pun">);</span><span class="pln">
      jsonObject</span><span class="pun">.</span><span class="pln">put</span><span class="pun">(</span><span class="str">"Date_Of_Birth"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"1989-09-26"</span><span class="pun">);</span><span class="pln">
      jsonObject</span><span class="pun">.</span><span class="pln">put</span><span class="pun">(</span><span class="str">"Place_Of_Birth"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"Vishakhapatnam"</span><span class="pun">);</span><span class="pln">
      jsonObject</span><span class="pun">.</span><span class="pln">put</span><span class="pun">(</span><span class="str">"Country"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"25000"</span><span class="pun">);</span><span class="pln">
      </span><span class="com">//Creating a json array</span><span class="pln">
      </span><span class="typ">JSONArray</span><span class="pln"> array </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">JSONArray</span><span class="pun">();</span><span class="pln">
      array</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="str">"e-mail: krishna_kasyap@gmail.com"</span><span class="pun">);</span><span class="pln">
      array</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="str">"phone: 9848022338"</span><span class="pun">);</span><span class="pln">
      array</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="str">"city: Hyderabad"</span><span class="pun">);</span><span class="pln">
      array</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="str">"Area: Madapur"</span><span class="pun">);</span><span class="pln">
      array</span><span class="pun">.</span><span class="kwd">add</span><span class="pun">(</span><span class="str">"State: Telangana"</span><span class="pun">);</span><span class="pln">
      </span><span class="com">//Adding array to the json object</span><span class="pln">
      jsonObject</span><span class="pun">.</span><span class="pln">put</span><span class="pun">(</span><span class="str">"contact"</span><span class="pun">,</span><span class="pln">array</span><span class="pun">);</span><span class="pln">
      </span><span class="kwd">try</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
         </span><span class="typ">FileWriter</span><span class="pln"> file </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">FileWriter</span><span class="pun">(</span><span class="str">"E:/json_array_output.json"</span><span class="pun">);</span><span class="pln">
         file</span><span class="pun">.</span><span class="pln">write</span><span class="pun">(</span><span class="pln">jsonObject</span><span class="pun">.</span><span class="pln">toJSONString</span><span class="pun">());</span><span class="pln">
         file</span><span class="pun">.</span><span class="pln">close</span><span class="pun">();</span><span class="pln">
      </span><span class="pun">}</span><span class="pln"> </span><span class="kwd">catch</span><span class="pln"> </span><span class="pun">(</span><span class="typ">IOException</span><span class="pln"> e</span><span class="pun">)</span><span class="pln"> </span><span class="pun">{</span><span class="pln">
         </span><span class="com">// TODO Auto-generated catch block</span><span class="pln">
         e</span><span class="pun">.</span><span class="pln">printStackTrace</span><span class="pun">();</span><span class="pln">
      </span><span class="pun">}</span><span class="pln">
      </span><span class="typ">System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="str">"JSON file created: "</span><span class="pun">+</span><span class="pln">jsonObject</span><span class="pun">);</span><span class="pln">
   </span><span class="pun">}</span><span class="pln">
</span><span class="pun">}</span>

Output

JSON file created: {
"First_Name":"Krishna Kasyap",
"Place_Of_Birth":"Vishakhapatnam",
"Last_Name":"Bhagavatula",
"contact":[
"e-mail: krishna_kasyap@gmail.com",
"phone: 9848022338","city: Hyderabad",
"Area: Madapur",
"State: Telangana"],
"Country":"25000",
"ID":"1",
"Date_Of_Birth":"1989-09-26"}

If you observe the contents of the JSON file you can see the created data as ?