public boolean onOptionsItemSelected(MenuItem item) {
    int id = item.getItemId();

    if (id == R.id.nav_calendar) {
        Intent i=new Intent(this, Calendar.class);
        startActivity(i);
    }
    if (id == R.id.nav_info) {
        Intent i=new Intent(this, CarInfo.class);
        startActivity(i);
    }

    if (id == R.id.nav_expenses) {
        Intent i=new Intent(this, Expenses.class);
        startActivity(i);
    }
    if (id == R.id.nav_map) {
        Intent i=new Intent(this, Map.class);
        startActivity(i);
    }
    if (id == R.id.nav_service) {
        Intent i=new Intent(this, Service.class);
        startActivity(i);
    }

    return super.onOptionsItemSelected(item);
}