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Note that the output file is simply a text file with the extension .json . Thus it can be read by any program that is capable of reading plain text files.
Listing 6 also signals the end of the main method and the end of the program.
Figure 1 shows a "prettified" version of the contents of the output file.
{"game":
[{
"cards":[
"2-club","3-heart","4-diamond","5-spade"],"name":"Tom"
},{
"cards":[
"4-heart","5-heart","6-club","7-diamond"],"name":"Joe"
}]
} The actual contents of the file do not contain line breaks and indentation as shown in Figure 1 . Those cosmetic features were added manually to Figure 1 to make it easier for you to correlate the output with the code shown earlier. Instead, the actual file consists simply of a string ofcharacters that begins as shown in Figure 2 .
{"game":[{"cards":["2-club","3-heart","4-diamond","5-spade"],... As mentioned earlier, a later page in this book will read the JSON string from the file and decode it into its component parts. Figure 3 shows a preview of what you will see on that page.
First Player's Name: Tom
First Player's cards2-club
3-heart4-diamond
5-spadeSecond Player's Name: Joe
Second Player's cards4-heart
5-heart6-club
7-diamond Figure 3 shows the JSON string decoded and formatted into a display that is representative of the intent of the string -- to encapsulate information aboutthe players and their cards in a game of cards.
I encourage you to copy the code from Listing 7 . Execute the code and confirm that your output file matches that shown in Figure 2 . 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.
Listing 7 provides a complete listing of the program named Code.java .
/************************************************
Copyright: R.G.Baldwin 2016Revised: 06/01/16
Creates a json string and writes it to an outputfile. The json string contains an array, which in
turn contains two arrays.Tested with Java 8, Windows 7, and
json-simple-1.1.1.************************************************/
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");//Create and populate a json array, which is// a subclass of the Java ArrayList class.
JSONArray arrayListA = new JSONArray();arrayListA.add("2-club");
arrayListA.add("3-heart");arrayListA.add("4-diamond");
arrayListA.add("5-spade");//Populate the json object with a key/value// pair where the value is an array.
hashMapA.put("cards",arrayListA);//Create and populate another similar json// object.
JSONObject hashMapB = new JSONObject();hashMapB.put("name","Joe");JSONArray arrayListB = new JSONArray();
arrayListB.add("4-heart");arrayListB.add("5-heart");
arrayListB.add("6-club");arrayListB.add("7-diamond");
hashMapB.put("cards",arrayListB);//Create another json array and populate// it with the two json objects created
// earlier.JSONArray arrayListC = new JSONArray();
arrayListC.add(hashMapA);arrayListC.add(hashMapB);
//Create another json object and populate// it with a key/value pair where the value
// is the array from above.JSONObject hashMapC = new JSONObject();
hashMapC.put("game",arrayListC);try{//Encode the HashMap object into a
// json String and write it to an output// file. Note that it is simply a text file
// with a different extension.PrintWriter out =
new PrintWriter(new File("junk.json"));hashMapC.writeJSONString(out);
out.flush();}catch(IOException ex){
ex.printStackTrace();}//end catch
}//end main}//end class Code This section contains a variety of miscellaneous information.
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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