How to get json from website?

Question

Java

Here is the info_apps.java file code

package com.apps.new;

import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;

public class Info_apps extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_info_apps);

    }

        // Проверка обновлений
        public void onClick (View view){
        
            // Выводим
            Snackbar.make(view, "Данная функция в разработке.\nОбновляйте приложение на site.ru/app", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }

}

It is necessary that when the button onClickis clicked, the json version of the application on the server is checked, if the version is greater than the current one, then we display a confirmation for downloading.
Tried on org.json, the application is restarted when the button is clicked.
I can’t output any json at all, all the time there are some errors.