I want to add the values of checkbox in recyclerview

as u all can see ,if i check to my checkbox the price should appear below,beside the makepayment button if i check more than one check box addition should be perform and same way the subtraction

I have done something that gives me result on click of button ..but i want the dynamic check box

Adpter class:

holder.payment.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        CheckBox cb = (CheckBox) v;
        Buy_Data contact = (Buy_Data) cb.getTag();
        contact.setSelected(cb.isChecked());
        carsList.get(position).setSelected(cb.isChecked());
        Toast.makeText( v.getContext(),"Clicked on Checkbox: " + cb.getText() + " is "
                        + cb.isChecked(), Toast.LENGTH_SHORT).show();
    }
});

Mainclass of recyclerview:

makepayment=(Button)findViewById(R.id.makepayment);
makepayment.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View view) {

        ArrayList<Buy_Data> stList = ((Mts_Payment_Adapter)adapter).getStudentist();
        int a=0;
        for (int i = 0; i < stList.size(); i++)
        {
            Buy_Data singleStudent = stList.get(i);
            if (singleStudent.isSelected() == true)
            {
                a = a + Integer.parseInt(singleStudent.getPrice());
            }
            else
            {}
        }
        Toast.makeText(Mts_Payment.this, "Selected Students:" + a, 
        Toast.LENGTH_SHORT).show();
        total=(TextView)findViewById(R.id.aaa);
        total.setText(String.valueOf(a));
    }
});