Tukukkk

I have the following code that seems to work. I'm just wondering if I'm doing everything right or if there are some obvious improvements that should be made.

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.SQLException;

import java.sql.Statement;

import org.apache.commons.io.FileUtils;

import java.io.File;

import java.io.IOException;



public class DBtest{

    private static int cnt = 0;

    public static void main(String args) throws SQLException{

        System.out.print('u000C');

        String db = "test2";

        File file = new File(db);



        Connection conn = connectDB(db);

        close(conn);

        deleteDB(file);



        System.exit(0);

    }

    public static void close(Connection conn){

        try{ 

            if (conn != null) conn.close();

            System.out.println("Connection closed");

        }catch(SQLException e){            

            System.out.println("connection NOT closed " + e);

            System.exit(0);

        }        

    } 



    public static void deleteDB(File file) {      

        try{

            DriverManager.getConnection("jdbc:derby:;shutdown=true");                      

        }catch(SQLException e1){

            if(e1.getSQLState().equals("XJ015") && e1.getErrorCode() == 50000){

                 try{

                     FileUtils.deleteDirectory(file);

                }catch(IOException  e2){

                     System.out.println("FATAL ERROR: folder not deleted  " + e2); 

                     System.exit(0);

                }  

                 System.out.println("Database shutdown successful");

            }else{

                System.out.println("FATAL ERROR: Database not shutdown  " + e1);

                System.exit(0);

            }

        }

    } 



    public static Connection connectDB(String database) {

        Connection conn = null;

        try{ 

            File db = new File(database);

            String URL = "jdbc:derby:" + database + ";create=true"; 

            System.out.println("db exists " + db.exists());



            conn = DriverManager.getConnection(URL);            

            System.out.println("Succesfully connected to " + database);            

        }catch(SQLException e){

            System.out.println("FATAL ERROR: from getDB " + e);

            System.exit(0);            

        } 

        return conn;

    }    

}

Instead of appending strings with +, I strongly recommend you use String.format() to format your strings, especially when dealing with sensitive strings like database connections.

You can view documentation about it here: https://docs.oracle.com/javase/10/docs/api/java/util/Formatter.html

Another piece of advise - avoid "magic numbers" or "magic strings". You should not have random strings or numbers in your code which the reader of the code doesn't know the meaning of.

Some examples are: 50000 or XJ015.

These should be defined specifically as static final strings in your Java file, making it much easier to understand what it signifies.

As a last piece of advice, use System.out.err for errors rather than println. This allows you to see it in red in the console, being able to more easily identify an error.