Authorization to Google Client

I am writing a class for creating authorization to BigQuery and Google Cloud Storage.

In the past I have used CredentialStore which has been deprecated. I am trying to use DataStoreFactory but I discovered that it allows me to use only StoredCredential while I need a Credential.

I know one can convert from Credential to StoredCredential but I am not sure how to convert them in the opposite direction (StoredCredential to Credential). For example I am creating my connection like this:

Storage.Builder(HttpTransport transport,
    JsonFactory jsonFactory,
    HttpRequestInitializer httpRequestInitializer);

Could anyone point me in a direction about how to achieve this?

Thank you!