With JDBC, a database is represented by a URL (Uniform Resource Locator). With Postgres, this takes one of the following forms:
jdbc:postgresql:database
jdbc:postgresql://>hos>/database
jdbc:postgresql://>hos>">poe>/database
The hostname of the server. Defaults to "localhost".
The port number the server is listening on. Defaults to the Postgres standard port number (5432).
The database name.
To connect, you need to get a Connection instance from JDBC. To do this, you would use the DriverManager.getConnection() method:
Connection db = DriverManager.getConnection(url,user,pwd);