Android JSON data parsing showing into ListView

Activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.oshin.myjsonlist.MainActivity">

<ListView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:dividerHeight="3dp"
    android:divider="@color/colorPrimaryDark"
    android:id="@+id/l1"
></ListView>

</LinearLayout>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.oshin.myjsonlist">
    <uses-permission android:name="android.permission.INTERNET"></uses-permission>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

CustomAdapter.java

package com.example.oshin.myjsonlist;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

import java.util.List;

/**
 * Created by oshin on 1/30/2018.
 */

class CustomAdapter extends BaseAdapter{

      private Context applicationContext;
    private int sample;
    private List<JsonModel> jsonModels;


    CustomAdapter(Context applicationContext, int sample, List<JsonModel> jsonModels) {

                this.applicationContext =applicationContext;
                  this.sample = sample;
               this.jsonModels =jsonModels;

    }


    @Override
    public int getCount() {
        return jsonModels.size();
    }

    @Override
    public Object getItem(int i) {
        return jsonModels.get(i);
    }

    @Override
    public long getItemId(int i) {
        return i;
    }

    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {



        if(view == null)
        {
            LayoutInflater layoutInflater = (LayoutInflater) applicationContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

          view =  layoutInflater.inflate(R.layout.sample,viewGroup,false);

        }

        TextView name,grade,section;

        name= view.findViewById(R.id.name);
        grade=view.findViewById(R.id.grade);
        section=view.findViewById(R.id.section);


        name.setText(jsonModels.get(i).getName());
        grade.setText(jsonModels.get(i).getGrade());
        section.setText(jsonModels.get(i).getSection());

        return view;
    }
}

jsonModel.java

package com.example.oshin.myjsonlist;

/**
 * Created by oshin on 1/30/2018.
 */

public class JsonModel {


 private String name;
    private String grade;
    private  String section;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGrade() {
        return grade;
    }

    public void setGrade(String grade) {
        this.grade = grade;
    }

    public String getSection() {
        return section;
    }

    public void setSection(String section) {
        this.section = section;
    }
}

MainActivity.java

package com.example.oshin.myjsonlist;

import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ListView;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {


    private ListView l1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        l1 = (ListView) findViewById(R.id.l1);

        JsonWork jsonWork = new JsonWork();
        jsonWork.execute();
    }


    private class JsonWork extends AsyncTask<String,String,List<JsonModel>>{


        HttpURLConnection httpURLConnection = null;
       BufferedReader bufferedReader = null;
      String  FullJsonData;
        @Override
        protected List<JsonModel> doInBackground(String... strings) {

            try {
                URL url = new URL("https://api.myjson.com/bins/17ab25");
                httpURLConnection = (HttpURLConnection) url.openConnection();
                httpURLConnection.connect();
                InputStream inputStream = httpURLConnection.getInputStream();
                bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
                StringBuffer stringBuffer= new StringBuffer();
                String line="";

                while ((line= bufferedReader.readLine())!= null){

                    stringBuffer.append(line);

                }
                 FullJsonData =  stringBuffer.toString();
                List<JsonModel> jsonModelList = new ArrayList<>();

                JSONObject jsonStartingObject = new JSONObject(FullJsonData);
                JSONArray  jsonStudentArray = jsonStartingObject.getJSONArray("result");


                for(int i=0; i<jsonStudentArray.length(); i++) {

                    JSONObject jsonUnderArrayObject = jsonStudentArray.getJSONObject(i);

                    JsonModel jsonModel = new JsonModel();
                    jsonModel.setName(jsonUnderArrayObject.getString("name"));
                    jsonModel.setGrade(jsonUnderArrayObject.getString("grade"));
                    jsonModel.setSection(jsonUnderArrayObject.getString("section"));
                    jsonModelList.add(jsonModel);
                }

                return jsonModelList;


            } catch (JSONException | IOException e) {
                e.printStackTrace();
            } finally{

                httpURLConnection.disconnect();
                try {
                    bufferedReader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }

            return null;
        }

        @Override
        protected void onPostExecute(List<JsonModel> jsonModels) {
            super.onPostExecute(jsonModels);
          CustomAdapter adapter = new CustomAdapter(getApplicationContext(),R.layout.sample,jsonModels);
            l1.setAdapter(adapter);


        }
    }

}

sample.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margin="10dp"

    >

    <TextView
        android:id="@+id/name"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Name"
        android:textAlignment="center"
        android:textSize="30sp"
        android:textStyle="bold"
        android:background="@color/colorAccent"
        />

    <TextView
        android:id="@+id/grade"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="#ea8e8e"
        android:text="Grade"
        android:textAlignment="center"
        android:textSize="25sp"
        android:textStyle="bold" />

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="20sp"
        android:textStyle="bold"
        android:text="Section"
        android:id="@+id/section"
        android:textAlignment="center"
        android:background="#c29ef5"

        />
</LinearLayout>