JSON Parsing 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 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("63OH")
    
    // as we are calling data from array
    // so we are calling it with json object
    // and naming that method as getCourse();
    Call<RecyclerData> getCourse();
}

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

import androidx.appcompat.app.AppCompatActivity;
import androidx.cardview.widget.CardView;

import com.squareup.picasso.Picasso;

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

public class MainActivity extends AppCompatActivity {
    // creating variables for our textview,
    // imageview,cardview and progressbar.
    private TextView courseNameTV, courseTracksTV, courseBatchTV;
    private ImageView courseIV;
    private ProgressBar loadingPB;
    private CardView courseCV;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        // initializing our variables.
        loadingPB = findViewById(R.id.idLoadingPB);
        courseCV = findViewById(R.id.idCVCourse);
        courseNameTV = findViewById(R.id.idTVCourseName);
        courseTracksTV = findViewById(R.id.idTVTracks);
        courseBatchTV = findViewById(R.id.idTVBatch);
        courseIV = findViewById(R.id.idIVCourse);
        getCourse();
    }

    private void getCourse() {

        // 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);
        Call<RecyclerData> call = retrofitAPI.getCourse();
        call.enqueue(new Callback<RecyclerData>() {
            @Override
            public void onResponse(Call<RecyclerData> call, Response<RecyclerData> response) {
                if (response.isSuccessful()) {
                    // inside the on response method.
                    // we are hiding our progress bar.
                    loadingPB.setVisibility(View.GONE);
                    // in below line we are making our card
                    // view visible after we get all the data.
                    courseCV.setVisibility(View.VISIBLE);
                    RecyclerData modal = response.body();
                    // after extracting all the data we are
                    // setting that data to all our views.
                    courseNameTV.setText(modal.getCourseName());
                    courseTracksTV.setText(modal.getCourseTracks());
                    courseBatchTV.setText(modal.getCourseMode());
                    // we are using picasso to load the image from url.
                    Picasso.get().load(modal.getCourseimg()).into(courseIV);
                }
            }

            @Override
            public void onFailure(Call<RecyclerData> call, Throwable t) {
                // displaying an error message in toast
                Toast.makeText(MainActivity.this, "Fail to get the data..", Toast.LENGTH_SHORT).show();
            }
        });
    }
}