Querying for on-device acconuts

// From Plaid app [DesignerNewsLogin.class]

private void setupAccountAutocomplete() {
        if (ContextCompat.checkSelfPermission(this, Manifest.permission.GET_ACCOUNTS) ==
                PackageManager.PERMISSION_GRANTED) {
            permissionPrimer.setVisibility(View.GONE);
            final Account[] accounts = AccountManager.get(this).getAccounts();
            final Set<String> emailSet = new HashSet<>();
            for (Account account : accounts) {
                if (Patterns.EMAIL_ADDRESS.matcher(account.name).matches()) {
                    emailSet.add(account.name);
                }
            }
            username.setAdapter(new ArrayAdapter<>(this,
                    R.layout.account_dropdown_item, new ArrayList<>(emailSet)));
        } else {
            if (shouldShowRequestPermissionRationale(Manifest.permission.GET_ACCOUNTS)) {
                setupPermissionPrimer();
            } else {
                permissionPrimer.setVisibility(View.GONE);
                shouldPromptForPermission = true;
            }
        }
    }