I want to do this in Java.

But I am not sure about getting a Connection object without Database
is first created.

Because it is possible to use executeUpdate with
Create Database 'NewDB.fdb' user 'sysdba' password 'masterkey'
page_size 2048

before I can use above statement, I need to get the Connection to the
database which does not yet exist.

or

If someone knows how to do this using Service API / FBBackupManager, I
would appreciate the Source Code example.

Thanks,
Ashok