JsonParsing Using AsyncTask in Android

 Create One ServiceHandler Class for Manage Connection For JsonParsing

ServiceHandler.java

public class ServiceHandler {

    public String getstring(String url)
    {
        StringBuilder sb=new StringBuilder();
        String result;
        try{
           URL url1=new URL(url);
            HttpURLConnection con= (HttpURLConnection) url1.openConnection();
            InputStream in= new BufferedInputStream(con.getInputStream());
            BufferedReader br=new BufferedReader(new InputStreamReader(in));
            String line;
            while ((line=br.readLine())!=null)
            {
                sb.append(line+"\n");
            }
        }
        catch (Exception e)
        {

        }
        result=sb.toString();
        return result;
    }
}

public class MainActivity extends AppCompatActivity {

    ListView lv;
    String URLDATA="Enter URL";
    String CONTACT="contacts";
    String ID="id";
    String NAME="name";
    String EMAIL="email";
    ArrayList<User>arrayList;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv=findViewById(R.id.lstview);
        arrayList=new ArrayList<>();
        new Dataload().execute();
    }
    class Dataload extends AsyncTask<Void,Void,Void>
    {
        ProgressDialog pd;
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pd=new ProgressDialog(MainActivity.this);
            pd.setTitle("Loading data");
            pd.setMessage("Please Wait");
            pd.show();
        }

        @Override
        protected Void doInBackground(Void... voids) {
            try{
                ServiceHandler sh=new ServiceHandler();
                String result=sh.getstring(URLDATA);
                Log.e("Error",result);
                if(result!=null)
                {
                    JSONObject jsonObject=new JSONObject(result);
                    JSONArray jsonArray=jsonObject.getJSONArray(CONTACT);
                    for(int i=0;i<jsonArray.length();i++)
                    {
                        JSONObject obj=jsonArray.getJSONObject(i);
                        String id=obj.getString(ID);
                        String name=obj.getString(NAME);
                        String email=obj.getString(EMAIL);
                        User user=new User();
                        user.setId(id);
                        user.setName(name);
                        user.setEmail(email);
                        arrayList.add(user);
                    }
                }
            }
            catch (Exception e)
            {

            }
            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
            pd.dismiss();
            Customadpter customadpter = new Customadpter(MainActivity.this, arrayList);
            lv.setAdapter(customadpter);
        }
    }
}

public class Customadpter extends BaseAdapter {
    Context context;
    ArrayList<User> arrayList;

    public Customadpter(Context context, ArrayList<User> arrayList) {
        this.context = context;
        this.arrayList = arrayList;
    }

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

    @Override
    public Object getItem(int position) {
        return position;
    }

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

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        View v = inflater.inflate(R.layout.custom, null);
        TextView tv1 = v.findViewById(R.id.textView2);
        TextView tv2 = v.findViewById(R.id.textView3);
        TextView tv3 = v.findViewById(R.id.textView4);
        tv1.setText(arrayList.get(position).getId() + "");
        tv2.setText(arrayList.get(position).getName());
        tv3.setText(arrayList.get(position).getEmail());
        return v;
    }
}


public class User {
    String id,name,email;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <ListView
        android:id="@+id/lstview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:layout_editor_absoluteX="1dp"
        tools:layout_editor_absoluteY="1dp" />
</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <TextView
            android:id="@+id/textView2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="TextView" />

        <TextView
            android:id="@+id/textView3"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="TextView" />

        <TextView
            android:id="@+id/textView4"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="TextView" />
    </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>