Java Arraylist Data extraction

Question

How would you extract the data as follows:

I want to extract from this arraylist:

[{itemname=Original, number=12}, {itemname=BBQ, number=23}, {itemname=CatchUp, number=23}]

This array:

{"Original":12,"BBQ":23,"CatchUp":23}

Thanks in advance! Here's the code used to generate the hashmap:

ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String,String>>();
for (int i = 0; i<7;i++) {
 HashMap<String,String> map = new HashMap<String,String>();
  map.put("itemname",chips[i]);
  map.put("number",chipentry[i]);
  list.add(map);
 }

Can you post any code to explain how you create the ArrayList? — David Oliván
– David Oliván, Commented Apr 8, 2011 at 8:39
What exactly is the content of the list and what exactly should be the content of the array? In terms of Java objects, please! — Joachim Sauer
– Joachim Sauer, Commented Apr 8, 2011 at 8:39
Your "array" appears to have compound elements which you've specified using colons. What exactly do you mean? What type would your array use? Or are you really talking about a map? — Jon Skeet
– Jon Skeet, Commented Apr 8, 2011 at 8:40
Sorry folks, yeah - it's an arraylist of hashmaps, and I want to convert it to JSON as c0mrade deduced — staeit
– staeit, Commented Apr 8, 2011 at 8:49

ant · Accepted Answer · 2011-04-08 08:44:28Z

5

It looks like you want to convert it to Json, using google gson http://code.google.com/p/google-gson/ its very easy

"Provide simple toJson() and fromJson() methods to convert Java objects to JSON and vice-versa"

Here is what I mean :

Gson gson = new Gson();
gson.toJson(map); //where map is your map object

answered Apr 8, 2011 at 8:44

ant

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1 Comment

staeit Over a year ago

Thank you c0mrade. I ended up creating a new JSONObject instead because this didn't get the quite exact format I wanted, but it helped me figure it out. cheers

ant · Accepted Answer · 2011-04-08 09:32:24Z

0

Thanks for the tip - I have changed to the following code:

  ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String,String>>();
  Gson gson = new Gson();
  for (int i = 0; i<7;i++) {
     HashMap<String,String> map = new HashMap<String,String>();
     map.put("itemname",chips[i]);
     map.put("number",chipentry[i]);
     list.add(map);
     System.out.println(gson.toJson(map));
  }

And the result is https://i.sstatic.net/b1qg4.png

I imported com.google.gson.Gson, is there something else I'm missing? Please excuse my newbness and thanks for the help!

edited Apr 8, 2011 at 9:32

ant

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answered Apr 8, 2011 at 9:21

staeit

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4 Comments

ant Over a year ago

I've edited your answer, this will print each map converted to json in your arraylist

staeit Over a year ago

from this it looks like it's generating 7 JSON object instead of one single - is there a way to combine the JSON objects together and store in a variable?

ant Over a year ago

yes, convert the whole list to json instead, gson.toJson(list);

staeit Over a year ago

@c0mrade: thanks, now one last thing - instead of getting the desired format of [{"Original":12,"BBQ":23,"CatchUp":23}] I obtain this: [{"itemname":"Original","number","12"},{"itemname":"BBQ","number":"23"},{"itemname":"CatchUp","number":"23"}]. What do I need to change in my code to get the desired format?

Chathuranga Withana · Accepted Answer · 2011-04-08 17:01:34Z

0

To extract the data as you expected, you can use Jackson JSON processor. It allows you to read and write JSON easily. You can follow their tutorial here.

Fist you have to download the relevant jar files(2 files) provided by them.

So the following code snippet should solve your problem, and the result is written to the jsonResult.json file.

    String[] chips = {"Original", "BBQ", "CatchUp"};
    String[] chipentry = {"12", "23", "23"};

    List<HashMap<String, String>> list = new ArrayList<HashMap<String, String>>();
    for (int i = 0; i < 3; i++) {
        HashMap<String, String> map = new HashMap<String, String>();
        map.put("itemname", chips[i]);
        map.put("number", chipentry[i]);
        list.add(map);
    }

    ObjectMapper mapper = new ObjectMapper();
    Map<String, Object> untyped = new HashMap<String, Object>();

    untyped.put("result", list);
    mapper.writeValue(new File("jsonResult.json"), untyped);

And following is the output of the file,

{"result":[{"itemname":"Original","number":"12"},{"itemname":"BBQ","number":"23"},{"itemname":"CatchUp","number":"23"}]}

answered Apr 8, 2011 at 17:01

Chathuranga Withana

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2 Comments

staeit Over a year ago

Thank you Chathuranga, it's not quite what I was looking for but it helped me out. I can only accept one answer but again, much appreciated.

Chathuranga Withana Over a year ago

:) its ok staeit... anyway if you figure it out thats great.... if you are willing, you can share your final result as well... it can help others who faced the same issue... cheers!

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