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This code produces the screen output shown in Figure 4 .

Figure 4. Information about the second player. Second Player's Name: Joe Second Player's cards4-heart 5-heart6-club 7-diamond

The end of the program

Listing 6 signals the end of the main method and the end of the program.

Run the program

Click here to download a zip file containing a JSON data file named junk.json that can be used to experiment with this program.

I encourage you to copy the code from Listing 7 . Execute the code and confirm that you get the same results as those shown in Figure 1 through Figure 4 . Experiment with the code, making changes, and observing the results of your changes. Make certain that youcan explain why your changes behave as they do.

Complete program listing

A complete listing of the program named Code is provided in Listing 7 .

Listing 7 . The program named Code.java. /******************************************************************** Copyright: R.G.Baldwin 2016Revised: 06/01/16 Reads a json string from a file, parses, anddisplays some of its parts. Tested with Java 8, Windows 7, andjson-simple-1.1.1. ********************************************************************/import org.json.simple.JSONObject; import org.json.simple.JSONArray;import org.json.simple.JSONValue; import java.io.IOException;import java.io.FileReader; import java.util.*;class Code{ public static void main(String[]args){ //Instantiate a JSONObject object, which is a subclass of the// Java HashMap class. JSONObject jsonMap = null;try{ //Read json string from a file and parse it into a HashMap.jsonMap = (JSONObject)(JSONValue.parse(new FileReader("junk.json")));}catch(IOException ex){ ex.printStackTrace();}//end catch //Get and display the json stringSystem.out.println("json string: " + jsonMap); System.out.println();//blank line//Get the game array into an ArrayList object. JSONArray gameArrayList = (JSONArray)jsonMap.get("game");//Get and display info about the first player.JSONObject firstPlayerMap = (JSONObject)gameArrayList.get(0); System.out.println("First Player's Name: " +firstPlayerMap.get("name"));JSONArray firstPlayerCardsList = (JSONArray)firstPlayerMap.get("cards");System.out.println("First Player's cards"); Iterator<String>iterator = firstPlayerCardsList.iterator(); while (iterator.hasNext()) {System.out.println(iterator.next()); }//end while loop//Get and display info about the second player. System.out.println();JSONObject secondPlayerMap = (JSONObject)gameArrayList.get(1); System.out.println("Second Player's Name: " +secondPlayerMap.get("name"));JSONArray secondPlayerCardsList = (JSONArray)secondPlayerMap.get("cards");System.out.println("Second Player's cards"); iterator = secondPlayerCardsList.iterator();while (iterator.hasNext()) { System.out.println(iterator.next());}//end while loop }//end main}//end class Code

Miscellaneous

This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: Json0230: Decoding JSON Arrays
  • File: Json0230.htm
  • Published: 06/01/16
Disclaimers:

Financial : Although the Connexions site makes it possible for you to download a PDF file for thismodule at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should beaware that some of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.com showing me as the author. Ineither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, please beaware that it is a copy of a module that is freely available on cnx.org and that it was made and published withoutmy prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.

-end-

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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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