import java.lang.System.*;
import java.nio.file.* ;
import java.sql.*;
import java.io.*;
import java.util.*;

public class TestDB {
    public static void main(String[] args) throws IOException {
         try {
            runTest();
        } catch (SQLException ex) {
            for (Throwable t : ex)
                t.printStackTrace();
        }
    }


    public static void runTest() throws SQLException, IOException {
        try (Connection conn = getConnection(); Statement stat = conn.createStatement()) {
            stat.executeUpdate("CREATE TABLE G (id BIGINT,name CHAR(20))");
            stat.executeUpdate("ALTER TABLE G  ALTER COLUMN id SET DEFAULT NEXTVAL('seq')");
            for( int i=0;i<5;i++)
            stat.executeUpdate("INSERT INTO public.g (id,name) VALUES(DEFAULT,'Hello, world2')");
           try (ResultSet result=stat.executeQuery("SELECT NEXTVAL('seq')"))
            {
                while(result.next())
                    System.out.println(result.getString(1));
            }
////stat.executeUpdate("DROP TABLE G");
    //        stat.executeUpdate("DROP TABLE Greetings");
        }
    }
    public static Connection getConnection()throws SQLException,IOException
    {
        Properties props=new Properties();
        try (InputStream in =
                     Files.newInputStream(Paths.get("Database.properties")))
        {
            props.load(in);
        }
        String drivers = props.getProperty("jdbc.drivers");
        if(drivers!=null)
        {
            System.setProperty("jdbc.drivers",drivers);
        }
        String url=props.getProperty("jdbc.url");
        String username = props.getProperty("jdbc.username");
        String password = props.getProperty("jdbc.password");

        return  DriverManager.getConnection(url,username,password);
    }
}