Java database

import java.util.*;



public class UserInterface
 {
    static UserInterface intFace = new UserInterface();
    static SongDatabase dataMain = new SongDatabase();
    public static String artist;
    public static String name;
    public static double duration;
    public static int fileSize;





    private void run() {



    }





    public static void main(String[] args){



            Scanner console = new Scanner(System.in);



            do
            {




                System.out.println("\t MENU");
                System.out.println("0 EXIT");
                System.out.println("1 IMPORT TRACK");
                System.out.println("2 SHOW ALL");

                int switchOption = console.nextInt();

            switch(switchOption)  {

                    case 0 :
                        System.out.println("Exiting");
                        break;
                    case 1 :
                        System.out.println("Adding new track");
                        userImport();
                        break;
                    case 2 :
                        System.out.println("Scanning file system");
                        showFileSystem();
                        break;
                    default:
                        System.out.println("Invalid option");
                        break;



            }
        }while(true);


    }


    public static void showFileSystem()
    {


        int check = 1;
        Scanner console = new Scanner(System.in);


        System.out.println("Welcome to the system file scanner!");
        System.out.println("Scan now? (0)=yes, (1)=no."); check = console.nextInt();

            if (check==0) {
                System.out.println("System contents:"+dataMain.dataSlotCheck());



            }else{ System.out.println("Exiting file scanner..");

                }



    }




    public  static void userImport()
    {
        String userin1;
        String userin2;
        double userin3;
        int userin4;





        Scanner console = new Scanner(System.in);
        Song songMain = new Song();



        System.out.println("Welcome to the music importer!");
        System.out.println("Music can be imported in the format Artist:TrackName:Duration(mm.ss):FIleSize(kb)");
        System.out.println("Enter the artist:.."); userin1 = console.nextLine();
        System.out.println("Enter the track title:.."); userin2 = console.nextLine();
        System.out.println("Enter the duration:.."); userin3 = console.nextDouble();
        System.out.println("Enter the file size:.."); userin4 = console.nextInt();

        intFace.importAssign(userin1, userin2, userin3, userin4);

        dataMain.addSong();


        songMain.returnData();





    }

    public void importAssign(String userin1, String userin2, double userin3, int userin4) {

        intFace.artist = userin1;
        intFace.name = userin2;
        intFace.duration = userin3;
        intFace.fileSize = userin4;

    }

}



__________________________________________________________________________________________


public class SongDatabase
{

    UserInterface intFace = new UserInterface();
    Song Set = new Song();
    private Song a = new Song();
    private Song b = new Song();
    private Song c = new Song();
    private Song d = new Song();



    public void addSong()
    {





        if (a.songfileSize==0) {

                        setData(a.songartist, a.songname, a.songduration, a.songfileSize);

                    } else if (b.songfileSize==0) {

                        setData(b.songartist, b.songname, b.songduration, b.songfileSize);

                    } else if (c.songfileSize==0) {

                        setData(c.songartist, c.songname, c.songduration, c.songfileSize);

                    } else if (d.songfileSize==0) {

                        setData(c.songartist, c.songname, c.songduration, c.songfileSize);

                    } else {
                        System.out.println("Error: there is no free space in the database");
                    }





    }


    public void setData( String artist, String name, double duration, int fileSize)
    {
        Set.setArtist(intFace.artist);
        Set.setName(intFace.name);
        Set.setDuration(intFace.duration);
        Set.setFileSize(intFace.fileSize);
    }

    public String dataSlotCheck()
    {
        String finalScan;

        if (a.songfileSize==0 && b.songfileSize==0 && c.songfileSize==0 && d.songfileSize==0) {
            finalScan=("There is no music stored in the database.");
        }
        else if (d.songfileSize==0 && c.songfileSize==0 && b.songfileSize==0) {
            finalScan=("SlotA:"+a.songartist+":"+a.songname+":"+a.songduration+":"+a.songfileSize);
        } else if (d.songfileSize==0 && c.songfileSize==0) {
            finalScan= ("SlotA:"+a.songartist+":"+a.songname+":"+a.songduration+":"+a.songfileSize+
            "SlotB:"+b.songartist+":"+b.songname+":"+b.songduration+":"+b.songfileSize);
        } else if (d.songfileSize==0) {
            finalScan= ("SlotA:"+a.songartist+":"+a.songname+":"+a.songduration+":"+a.songfileSize+
             "SlotB:"+b.songartist+":"+b.songname+":"+b.songduration+":"+b.songfileSize+
             "SlotC:"+c.songartist+":"+c.songname+":"+c.songduration+":"+c.songfileSize);
        } else {
            finalScan= ("SlotA:"+a.songartist+":"+a.songname+":"+a.songduration+":"+a.songfileSize+
             "SlotB:"+b.songartist+":"+b.songname+":"+b.songduration+":"+b.songfileSize+
             "SlotC:"+c.songartist+":"+c.songname+":"+c.songduration+":"+c.songfileSize+
             "SlotD:"+d.songartist+":"+d.songname+":"+d.songduration+":"+d.songfileSize);
        }

        return (finalScan);

    }
}


________________________________________________________________________________________________

public class Song
{



        public Song(){
            /*Artist;
               * TrackName;
                 * Duration(mm:ss);
                   * fileSize(kB);*/
         }

       UserInterface intFace = new UserInterface();
       String songartist = intFace.artist;
       String songname = intFace.name;
       double songduration = intFace.duration;
       int songfileSize = intFace.fileSize;


        public void Song(String artist, String name, double duration, int fileSize){

           this.artist=artist;
           this.name=name;
           this.duration=duration;
           this.fileSize=fileSize;


         }

        public void setArtist(String newArtist)
        {

            artist = newArtist;

        }

        public String getArtist()
        {



            return artist;
        }

        public void setName(String newName)
        {

            name = newName;

        }

        public String getName()
        {



            return name;
        }

        public void setDuration(double newDuration)
        {

            duration = newDuration;

        }

        public double getDuration()
        {



            return duration;
        }

        public void setFileSize(int newFileSize)
        {

            fileSize = newFileSize;

        }

        public int getFileSize()
        {



            return fileSize;
        }

        public String returnData()
        {

            return ("You have imported: "+intFace.name+" By: "+intFace.artist+" || "
            +intFace.duration+"(mm.ss), "+intFace.fileSize+"(kB)");

        }
    }