How to add subcategories to given categories in the spinner?

See more:

Java

Android

ListView

spinner

I have created a spinner having categories, and now I want to add the doctor's name in the subcategories, but I am not able to do it.

What I have tried:

       String[] categories = {"All","Surgeon","Pediatrician","Cardiologist","Dermatologist"};
        ArrayAdapter aa = new ArrayAdapter(this,android.R.layout.simple_spinner_item,categories);
        aa.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
//Setting the ArrayAdapter data on the Spinner
        drspin.setAdapter(aa);
        drspin.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
                String a = drspin.getSelectedItem().toString();
                sd.setText(a);


            }

            @Override
            public void onNothingSelected(AdapterView<?> parent) {

            }
        });