Formatação de placa

final EditText plateEditText = (EditText) findViewById(R.id.plate_edit_text);
plateEditText.addTextChangedListener(new TextWatcher() {
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }
    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
    }
    @Override
    public void afterTextChanged(Editable s) {
        final String plate = s.toString();
        if (plate.length() == 7) {
            String plateFormatted = plate.substring(0, 3) + "-" + plate.substring(3, 7);
            plateEditText.setText(plateFormatted);
            plateEditText.setSelection(plateFormatted.length());
        }
    }
});