How to Extract Data from JSON Array in Android using Retrofit Library?

public class RecyclerData {
    // string variables for our data
    // make sure that the variable name
    // must be similar to that of key value
    // which we are getting from our json file.
    private String courseName;
    private String courseimg;
    private String courseMode;
    private String courseTracks;

    public String getCourseName() {
        return courseName;
    }

    public void setCourseName(String courseName) {
        this.courseName = courseName;
    }

    public String getCourseimg() {
        return courseimg;
    }

    public void setCourseimg(String courseimg) {
        this.courseimg = courseimg;
    }

    public String getCourseMode() {
        return courseMode;
    }

    public void setCourseMode(String courseMode) {
        this.courseMode = courseMode;
    }

    public String getCourseTracks() {
        return courseTracks;
    }

    public void setCourseTracks(String courseTracks) {
        this.courseTracks = courseTracks;
    }

    public RecyclerData(String courseName, String courseimg, String courseMode, String courseTracks) {
        this.courseName = courseName;
        this.courseimg = courseimg;
        this.courseMode = courseMode;
        this.courseTracks = courseTracks;
    }
}

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

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.squareup.picasso.Picasso;

import java.util.ArrayList;

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.RecyclerViewHolder> {

    // creating a variable for our array list and context.
    private ArrayList<RecyclerData> courseDataArrayList;
    private Context mcontext;

    // creating a constructor class.
    public RecyclerViewAdapter(ArrayList<RecyclerData> recyclerDataArrayList, Context mcontext) {
        this.courseDataArrayList = recyclerDataArrayList;
        this.mcontext = mcontext;
    }

    @NonNull
    @Override
    public RecyclerViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // Inflate Layout
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.card_layout, parent, false);
        return new RecyclerViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerViewHolder holder, int position) {
        // Set the data to textview from our modal class.
        RecyclerData modal = courseDataArrayList.get(position);
        holder.courseNameTV.setText(modal.getCourseName());
        holder.courseTracksTV.setText(modal.getCourseTracks());
        holder.courseModeTV.setText(modal.getCourseMode());
        Picasso.get().load(modal.getCourseimg()).into(holder.courseIV);
    }

    @Override
    public int getItemCount() {
        // this method returns the size of recyclerview
        return courseDataArrayList.size();
    }

    // View Holder Class to handle Recycler View.
    public class RecyclerViewHolder extends RecyclerView.ViewHolder {
        // creating variables for our views.
        private TextView courseNameTV, courseModeTV, courseTracksTV;
        private ImageView courseIV;

        public RecyclerViewHolder(@NonNull View itemView) {
            super(itemView);
            // initializing our views with their ids.
            courseNameTV = itemView.findViewById(R.id.idTVCourseName);
            courseModeTV = itemView.findViewById(R.id.idTVBatch);
            courseTracksTV = itemView.findViewById(R.id.idTVTracks);
            courseIV = itemView.findViewById(R.id.idIVCourse);
        }
    }
}

import java.util.ArrayList;

import retrofit2.Call;
import retrofit2.http.GET;

public interface RetrofitAPI {

    // as we are making get request so we are displaying
    // GET as annotation.
    // and inside we are passing last parameter for our url.
    @GET("WO6S")
    
    // as we are calling data from array so we are calling
    // it with array list and naming that method as getAllCourses();
    Call<ArrayList<RecyclerData>> getAllCourses();
}

import android.os.Bundle;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import java.util.ArrayList;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MainActivity extends AppCompatActivity {
    
    // creating a variable for recycler view, 
    // array list and adapter class.
    private RecyclerView courseRV;
    private ArrayList<RecyclerData> recyclerDataArrayList;
    private RecyclerViewAdapter recyclerViewAdapter;
    private ProgressBar progressBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
       
        // initializing our variables.
        courseRV = findViewById(R.id.idRVCourse);
        progressBar = findViewById(R.id.idPBLoading);
       
        // creating new array list.
        recyclerDataArrayList = new ArrayList<>();
        
        // calling a method to
        // get all the courses.
        getAllCourses();
    }

    private void getAllCourses() {
        // on below line we are creating a retrofit
        // builder and passing our base url
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://jsonkeeper.com/b/")
                // on below line we are calling add 
                // Converter factory as Gson converter factory.
                .addConverterFactory(GsonConverterFactory.create())
                // at last we are building our retrofit builder.
                .build();
        // below line is to create an instance for our retrofit api class.
        RetrofitAPI retrofitAPI = retrofit.create(RetrofitAPI.class);
       
        // on below line we are calling a method to get all the courses from API.
        Call<ArrayList<RecyclerData>> call = retrofitAPI.getAllCourses();

        // on below line we are calling method to enqueue and calling 
        // all the data from array list.
        call.enqueue(new Callback<ArrayList<RecyclerData>>() {
            @Override
            public void onResponse(Call<ArrayList<RecyclerData>> call, Response<ArrayList<RecyclerData>> response) {
                // inside on response method we are checking 
                // if the response is success or not.
                if (response.isSuccessful()) {
                    
                    // on successful we are hiding our progressbar.
                    progressBar.setVisibility(View.GONE);
                   
                    // below line is to add our data from api to our array list.
                    recyclerDataArrayList = response.body();
                    
                    // below line we are running a loop to add data to our adapter class.
                    for (int i = 0; i < recyclerDataArrayList.size(); i++) {
                        recyclerViewAdapter = new RecyclerViewAdapter(recyclerDataArrayList, MainActivity.this);
                        
                        // below line is to set layout manager for our recycler view.
                        LinearLayoutManager manager = new LinearLayoutManager(MainActivity.this);
                        
                        // setting layout manager for our recycler view.
                        courseRV.setLayoutManager(manager);
                       
                        // below line is to set adapter to our recycler view.
                        courseRV.setAdapter(recyclerViewAdapter);
                    }
                }
            }

            @Override
            public void onFailure(Call<ArrayList<RecyclerData>> call, Throwable t) {
                // in the method of on failure we are displaying a 
                // toast message for fail to get data.
                Toast.makeText(MainActivity.this, "Fail to get data", Toast.LENGTH_SHORT).show();
            }
        });
    }
}