I am trying to load spinner from json data using following code:
 @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ArrayList<String> items = getCountries("data.json");
    Spinner spinner = (Spinner)findViewById(R.id.spinnerStandard);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.second_layout,R.id.txtStandard,items);
    spinner.setAdapter(adapter);
}
private ArrayList<String> getCountries(String fileName){
    JSONArray jsonArray = null;
    ArrayList<String> cList = new ArrayList<String>();
    try {
        InputStream is = getResources().getAssets().open(fileName);
        int size = is.available();
        byte[] data = new byte[size];
        is.read(data);
        is.close();
        String json = new String(data, "UTF-8");
        jsonArray=new JSONArray(json);
        if (jsonArray != null) {
            for (int i = 0; i < jsonArray.length(); i++) {
                cList.add(jsonArray.getJSONObject(i).getString("standard"));
            }
        }
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }
    catch (JSONException je)
    {
        je.printStackTrace();
    }
    return cList;
}
My json data is,
[
{
    "name":"Manoj",
    "surname":"Jadhav",
    "age":"18",
    "div":"A",
    "standard":"7"
},
{
    "name":"Nilesh",
    "surname":"Patankar",
    "age":"17",
    "div":"B",
    "standard":"7"
},
{
    "name":"Gourav",
    "surname":"Patil",
    "age":"18",
    "div":"A",
    "standard":"8"
},
{
    "name":"Pushkar",
    "surname":"Ganpule",
    "age":"17",
    "div":"A",
    "standard":"7"
},
{
    "name":"Prashant",
    "surname":"Raut",
    "age":"18",
    "div":"A",
    "standard":"8"
},
{
    "name":"Nachiket",
    "surname":"Salvi",
    "age":"17",
    "div":"A",
    "standard":"7"
},
{
    "name":"Hiren",
    "surname":"Lakhmani",
    "age":"18",
    "div":"B",
    "standard":"6"
}
]
In json data I am having duplicate standard values as I want to load only unique values from json into spinner (like there are standard values are 7, 7, 8, 7, 8, 7, 6 and I want to show only 6, 7, 8 out of those duplicate values.)
I've tried googling for all the options and as many other variations as I can think of and can't find any useful results, so I'm obviously missing something.
What is correct way to remove duplicate values ?
 
     
     
     
     
     
     
     
    