host    all             userName        127.0.0.1/32            sspi
host    all             all             127.0.0.1/32            md5

String url = "jdbc:postgresql://127.0.0.1:5432/dbName";
Connection conn = DriverManager.getConnection(url);
System.out.println(conn.isValid(10));

String url = "jdbc:postgresql://127.0.0.1:5432/dbName?gsslib=sspi"

Connection conn = DriverManager.getConnection(url, props) //where props have only username.

Connection conn = DriverManager.getConnection(url, "userName", ""); //empty password.