eliminar.java

btnEliminar.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        String indice = editTextIndice.getText().toString();
        if (indice.isEmpty()) {
            Toast.makeText(MainActivity.this, "Escribe el índice", Toast.LENGTH_SHORT).show();
            return;
        }
        adaptadorRecyclerView.eliminar(Integer.valueOf(indice));
    }
});