DatabaseHelper myDb;
myDb = new DatabaseHelper(this);

@Override
    public void onBindViewHolder(homeAdapter.ViewHolder holder, int position) {
        holder.homeAuth.setText(authList.get(position));
        holder.homeName.setText(nameList.get(position));
        holder.homeIntro.setText(introList.get(position));
        holder.homePk.setText(pkList.get(position));

        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                final Context context = v.getContext();
                final String serverURL = "http://youngh.cafe24app.com/qrock/views/qrock_pk/user_email";

                myDb = new DatabaseHelper(this);  //is it Possible?
                final String token = myDb.getToken();
                final String email = myDb.getEmail();

                Intent myIntent = new Intent(context, mainActivity.class);
                context.startActivity(myIntent);
                ((Activity) context).finish();

                ((Activity) context).overridePendingTransition(R.xml.madefadein, R.xml.splashfadeout);
            }
        });
    }

DatabaseHelper myDb;
myDb = new DatabaseHelper(context);

class YourAdapter extends RecyclerView.Adapter<YourViewHolder>{
   private DatabaseHelper myDb;

   public YourAdapter(Context context){
      myDb = new DatabaseHelper(context)
   }
}