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Learn how to encode JSON array data using the JSONArray class. Also learn how to write an encoded JSON string to an output text file for transport to a different computing environment.

Revised: Thu Jun 02 19:27:08 CDT 2016

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Table of contents


This is a page from the book titled The json-simple Java Library . The book explains how to use the json-simple Java library to generate, transform, and query JSON text. This page explains how to encode JSON array data using the JSONArray class. It also shows how to write an encoded JSON string to an output text file for transport to a different programmingenvironment.

Viewing tip

I recommend that you open another copy of this module in a separate browser window and use the following links to easily find and view the Figuresand Listings while you are reading about them.


  • Figure 1 . Prettified version of output file contents.
  • Figure 2 . Beginning of output file contents.
  • Figure 3 . Decoded output data.


  • Listing 1 . Beginning of the class and the main method.
  • Listing 2 . Instantiate and populate a JSONArray object.
  • Listing 3 . Populate hashMapA.
  • Listing 4 . Create and populate another similar JSON object.
  • Listing 5 . Put the players in the game.
  • Listing 6 . Write the JSON string to an output file.
  • Listing 7 . The program named Code.java.

General background information

As you learned in the page titled Json0210: Structure of the json-simple Java Library , the JSONArray class extends the standard Java ArrayList class. Once you have an object of the JSONArray class, you have access to all of the methods defined in and inherited into the JSONArray class.

The sample program that follows will use the JSONArray class to construct a JSON string containing nested arrays and will then write thestring to an output file suitable for transport to a different programming environment.

A later page in this book will read the JSON string from the file and decode it into its component parts.

Discussion and sample code

The program named Code (see Listing 7 ) creates a JSON string and writes it to an output file. The json string contains an array, which in turn contains two nested arrays.

Beginning of the class and the main method

I will discuss and explain the program in fragments. The first fragment is shown in Listing 1 .

Listing 1 . Beginning of the class and the main method. import org.json.simple.JSONObject; import org.json.simple.JSONArray;import java.io.PrintWriter; import java.io.File;import java.io.IOException; class Code{public static void main(String[] args){//Create a json object. which is a subclass // of the Java HashMap class.JSONObject hashMapA = new JSONObject();//Populate the json object with a key/value // pair.hashMapA.put("name","Tom");

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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Damian Reply
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s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
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for screen printed electrodes ?
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s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
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