Android, JSON array into ArrayList<String>

Question

How to parse JSON string array into Java arraylist

I have this json:

{
"a": [
 "A-lore ipsum 1",
 "A-lore ipsum 2",
 "A-lore ipsum 3"
],
"b": [
 "B-lore ipsum 1", 
 "B-lore ipsum 2",
 "B-lore ipsum 3"
]
}

this is my original code :

//v refers to **a or b**
public ArrayList getJSON(String v){
 ArrayList<String> list = new ArrayList<String>();
 InputStream is = getResources().openRawResource(R.raw.myjson);
 Writer writer = new StringWriter();
 char[] buffer = new char[1024];
 Reader reader = null;
 try {
 reader = new BufferedReader(new InputStreamReader(is, "UTF-8"));
 int n;
 while ((n = reader.read(buffer)) != -1) {
 writer.write(buffer, 0, n);
 }
 String json = writer.toString();
 JSONObject jsonObject = new JSONObject(json);
 list = jsonObject.getString(v); //how to create list according to category
 } catch (Exception e) { e.printStackTrace();}
 return list;
}

So I would like my list to look like:
if v = 'a';

list = {"A-lore ipsum 1","A-lore ipsum 2","A-lore ipsum 3"};

if v = 'b';

list = {"B-lore ipsum 1","B-lore ipsum 2","B-lore ipsum 3"};

• Theresa: What were the results when you ran this code? You can edit your question to add the results.
• tziuka: I edited my post, take a look now.
• beresfordt: Having seen your update I fell my answer still meets your requirements, just change the method signature of getJSON to return SomeClass. Also jackson allows you to process the reader directly by calling mapper.readValue(reader, SomeClass.class); the caller knows which list they want, so can call getA/B on the object they are returned
• tziuka: It seams complicated to me, with another class. I would like to use org.json. and some simple method that return a list of strings
• beresfordt: I've added an answer which returns a List<String>, and uses org.json. I would strongly reccommend trying out jackson or gson however

Answer 1

public class MainActivity extends ActionBarActivity {
 private String TAG = MainActivity.class.getSimpleName();
 private TextView textView;
 ArrayList<String> arrayListA = new ArrayList<String>();
 ArrayList<String> arrayListB = new ArrayList<String>();
 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_main);
 textView = (TextView) findViewById(R.id.textView);
 try {
 InputStream is = getAssets().open("myfile.json");
 int size = is.available();
 byte [] byteArray = new byte[size];
 is.read(byteArray);
 is.close();
 String json = new String(byteArray, "UTF-8");
 try {
 JSONObject jsonObject = new JSONObject(json);
 JSONArray arrayA = jsonObject.getJSONArray("a");
 JSONArray arrayB = jsonObject.getJSONArray("b");
 for (int i = 0 ; i < arrayA.length(); i++) {
 String str = (String) arrayA.get(i);
 arrayListA.add(str);
 }
 for (int i = 0 ; i < arrayB.length(); i++) {
 String str = (String) arrayB.get(i);
 arrayListB.add(str);
 }
 for (String str : arrayListA) 
 Log.d(TAG, "strA : "+str);
 for (String str : arrayListB) 
 Log.d(TAG, "strB : "+str);
 } catch (JSONException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
 }
 } catch (IOException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
 }
 }
}

Answer 2

Op has updated the question specifying that org.json is to be used, and either array or list needs to be returned.

I would strongly recommend using a more fully featured json library such as jackson - see Android, JSON array into ArrayList<String> for a jackson way of doing this

The below will achieve what you want with json simple, however as you can see there is some fragility which using the org.json library introduces:

final JSONObject jsonObject = new JSONObject(json);
final JSONArray a = (JSONArray) jsonObject.get("a");
final List<String> returnArray = new ArrayList<>();
for (int i = 0; i < a.length(); i++) {
 returnArray.add((String)a.get(i));
}
return returnArray;

Answer 3

You have a syntax error in the json you have provided above; there should be a comma between a and b:

{
 "a": [
 "A-lore ipsum 1",
 "A-lore ipsum 2",
 "A-lore ipsum 3"
 ],
 "b": [
 "B-lore ipsum 1",
 "B-lore ipsum 2",
 "B-lore ipsum 3"
 ]
}

For parsing json I'd recommend using Jackson (or Gson) rather than the org.json library; I find them nicer to interact with.

The jackson wiki is at http://wiki.fasterxml.com/JacksonHome and has lots of tutorials etc

using jackson it would be:

ObjectMapper mapper = new ObjectMapper();
final SomeClass someClass = mapper.readValue(json, SomeClass.class);
List<String> a = someClass.getA();

where SomeClass is

class SomeClass {
 @JsonProperty
 private List<String> a;
 @JsonProperty
 private List<String> b;
 public SomeClass() {
 }
 public List<String> getA() {
 return a;
 }
 public List<String> getB() {
 return b;
 }
}