File I/O Using Object Streams

Question

My program is supposed to be a Driving instructor program that allows someone to enter a Name and Lesson Number, and it will pull up the Date, and Comments that the lesson took place. The information is saved in a file with the person's name, and saved as an array. We are required to use Object Streams for the file i/o. The only part of the program that I don't have working is the actual file i/o. The large commented section that I have in the datamanager class is the notes from the professor on the board and I haven't removed them yet. There are 4 classes for this file.
The main class that creates the program and calls the other classes.
import java.awt.*;
import javax.swing.*;
public class main {
/** Creates a new instance of main */
public main() {
* @param args the command line arguments
public static void main(String[] args)
guiLayout labelFrame = new guiLayout(); // creates LabelFrame
labelFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE);
labelFrame.setSize(600, 200);
labelFrame.setVisible(true);
} The second class is the GUI class and event handler class.
import java.awt.*;
import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class guiLayout extends JFrame{
    private JPanel centertop;
    private JPanel centermiddle;
    private JPanel centerbottom;
    private JLabel dateLabel;
    private JLabel nameLabel;
    private JLabel lessonLabel;
    private JLabel commentsLabel;
    private JTextArea DateTextArea;
    private JTextArea NameTextArea;
    private JTextArea LessonTextArea;
    private JTextArea CommentsTextArea;
    private JButton Save;
    private JButton Retrieve;
    private String tempDay[];
    private DataManager DMO;
    /** Creates a new instance of guiLayout */
    public guiLayout()
        super("Drive Application");
        setLayout(new FlowLayout());
        dateLabel = new JLabel("Date (mm/dd/yy)");
        nameLabel = new JLabel("Name");
        lessonLabel = new JLabel("Lesson (1-10)");
        commentsLabel = new JLabel("Comments");
        DateTextArea = new JTextArea(1, 7);
        NameTextArea = new JTextArea(1, 15);
        LessonTextArea = new JTextArea(1, 2);
        CommentsTextArea = new JTextArea(6, 30);
        Save = new JButton( "Save");
        Retrieve = new JButton( "Retrieve");
        //insert into GUI
        //TOP
        centertop = new JPanel();
        centertop.add(nameLabel);
        centertop.add(NameTextArea);
        centertop.add(lessonLabel);
        centertop.add(LessonTextArea);
        centertop.add(dateLabel);
        centertop.add(DateTextArea);
        centertop.setLayout(new GridLayout(6,1));
        add(centertop, BorderLayout.NORTH);
        centermiddle = new JPanel();
        centermiddle.setLayout(new GridLayout(1,1));
        centermiddle.add(CommentsTextArea);
        add(centermiddle, BorderLayout.CENTER);
        centerbottom = new JPanel();
        centerbottom.setLayout(new GridLayout(1,3));
        centerbottom.add (Save);
        centerbottom.add(Retrieve);
        add(centerbottom, BorderLayout.SOUTH);
        ButtonHandler handler = new ButtonHandler();
        Save.addActionListener( handler);
        Retrieve.addActionListener(handler);
    private class ButtonHandler implements ActionListener
        public void actionPerformed(ActionEvent event)
            String Namein = NameTextArea.getText();
            String Datein = DateTextArea.getText();
            String Commentsin = CommentsTextArea.getText();
            int Lessonin = Integer.parseInt(LessonTextArea.getText());
            if(event.getSource()==Save)
               DMO.Save(Namein, Datein, Commentsin, Lessonin);
            if(event.getSource()==Retrieve)
                if(Lessonin >= 1 && Lessonin <= 10)
                   LessonRecord r = (DMO.Retrieve(Namein, Lessonin));
                else
                    String errormess = "Lesson Number must be between 1 and 10!";
                    CommentsTextArea.setText(errormess);
}The third class is the DataManager class which handles the actual file i/o.
import java.io.*;
import java.util.*;
public class DataManager implements Serializable
    //private String Path = "P:\\D00766703\\CET431\\Assign5";
    private String Path = "C:\\Java";
    FileInputStream fin;
    FileOutputStream fout;
    ObjectInputStream oin;
    ObjectOutputStream oout;
    public String Retrieve(String name, int lesson)
        String itemFile = Path + name + ".ser";
        File f = new File(itemFile);
        if (f.exists() == true)
            try
                if(fin == null)
                    fin = new FileInputStream(itemFile);
                    oin = new ObjectInputStream(fin);
                LessonRecord r[] = oin.readObject();
                if(fin.available() == 0)
                    oout.close();
                    fout.close();
                    return r[lesson - 1];
            catch(IOException ioe)
                System.out.print(ioe);
        else
            LessonRecord LR = new LessonRecord();
            LR.date = " ";
            LR.comment = "File Not Found";
            return LR;
    /*create file object for Path\\Name
     *if file exists
     *  create fileinputstream
     *  create objectinputstream - oin
     *  read array of lesson records
     *  LessonRecord |r[] = oin.readObject();    need cast to array here
     *  close object input stream and file input stream
     *  return |r[lesson - 1];
     *else file does NOT EXIST
     *  LessonRecord LR = new LessonRecord();
     *  LR.date = " ";
     *  LR.comment = error message;
     *  return LR;
    public void Save(String name, String date, String comment, int lesson)
        String itemFile = Path + name + ".ser";
        File f = new File(itemFile);
        LessonRecord |r[];
        if (f.exists() == true)
            try
                fin = new FileInputStream(itemFile);
                oin = new ObjectInputStream(fin);
                LessonRecord r[] = oin.readObject();
            catch(IOException ioe)
                System.out.print(ioe);
        else
            r = new LessonRecord[10];
        r[lesson - 1] = new LessonRecord(date, comment);
        fout = new FileOutputStream(itemFile, true);
        oout = new ObjectOutputStream(fout);
        oout.write(r);
        oout.close();
        fout.close();
    /*create file object for Path\\Name
     *LessonRecord |r[];
     *if file exists
     *  create fileinputstream
     *  create objectinputstream - oin
     *  read array of lesson records
     *  LessonRecord |r[] = oin.readObject();    need cast to array here
     *  close object input stream and file input stream
     *else
     *  |r = new LessonRecord[10];
     *|r[lesson - 1] = new LessonRecord(date, comment);
     *createfileoutputstream(BaseDir\\Name);
     *createobjectoutputstream - oout
     *oout.write(|r);
     *closeobjectstream
     *closefilestream
}And the fourth class is the LessonRecord class which is serializable and has the date and comments variables.
import java.io.Serializable;
public class LessonRecord implements Serializable
    public String Date;
    public String Comment;
    /** Creates a new instance of LessonRecord */
    public LessonRecord()
        Date = "";
        Comment = "";
    public LessonRecord(String Datein, String Commentin)
        Date = Datein;
        Comment = Commentin;
}I could have sworn that the professor said to make it |r for the account records variable names, but I always get errors when I do that, and I need to know how to cast to an array too.

Answer 1

hi Friend,
I have made some modification to your code. and try this...I think it will help you...
/*guiLayout.java*/
import java.awt.*;
import javax.swing.*;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class guiLayout extends JFrame{
    private JPanel centertop;
    private JPanel centermiddle;
    private JPanel centerbottom;
    private JLabel dateLabel;
    private JLabel nameLabel;
    private JLabel lessonLabel;
    private JLabel commentsLabel;
    private JTextArea DateTextArea;
    private JTextArea NameTextArea;
    private JTextArea LessonTextArea;
    private JTextArea CommentsTextArea;
    private JButton Save;
    private JButton Retrieve;
    private String tempDay[];
    private DataManager DMO;
    /** Creates a new instance of guiLayout */
    public guiLayout()
        super("Drive Application");
        DMO=new DataManager();
        setLayout(new FlowLayout());
        dateLabel = new JLabel("Date (mm/dd/yy)");
        nameLabel = new JLabel("Name");
        lessonLabel = new JLabel("Lesson (1-10)");
        commentsLabel = new JLabel("Comments");
        DateTextArea = new JTextArea(1, 7);
        NameTextArea = new JTextArea(1, 15);
        LessonTextArea = new JTextArea(1, 2);
        CommentsTextArea = new JTextArea(6, 30);
        Save = new JButton( "Save");
        Retrieve = new JButton( "Retrieve");
        //insert into GUI
        //TOP
        centertop = new JPanel();
        centertop.add(nameLabel);
        centertop.add(NameTextArea);
        centertop.add(lessonLabel);
        centertop.add(LessonTextArea);
        centertop.add(dateLabel);
        centertop.add(DateTextArea);
        centertop.setLayout(new GridLayout(6,1));
        add(centertop, BorderLayout.NORTH);
        centermiddle = new JPanel();
        centermiddle.setLayout(new GridLayout(1,1));
        centermiddle.add(CommentsTextArea);
        add(centermiddle, BorderLayout.CENTER);
        centerbottom = new JPanel();
        centerbottom.setLayout(new GridLayout(1,3));
        centerbottom.add (Save);
        centerbottom.add(Retrieve);
        add(centerbottom, BorderLayout.SOUTH);
        ButtonHandler handler = new ButtonHandler();
        Save.addActionListener( handler);
        Retrieve.addActionListener(handler);
    private class ButtonHandler implements ActionListener
        public void actionPerformed(ActionEvent event)
            String Namein = NameTextArea.getText();
            int Lessonin = Integer.parseInt(LessonTextArea.getText());
            if(event.getSource()==Save)
                String Datein = DateTextArea.getText();
                 String Commentsin = CommentsTextArea.getText();
               DMO.Save(Namein, Datein, Commentsin, Lessonin);
            if(event.getSource()==Retrieve)
                if(Lessonin >= 1 && Lessonin <= 10)
                   LessonRecord r = (DMO.Retrieve(Namein, Lessonin));
                   System.out.println("Retrieve:"+ r.Comment+":"+r.Date);
                else
                    String errormess = "Lesson Number must be between 1 and 10!";
                    CommentsTextArea.setText(errormess);
/*DataManager.java*/
import java.io.*;
import java.util.*;
public class DataManager implements Serializable
    //private String Path = "P:\\D00766703\\CET431\\Assign5";
    private String Path = "C:/Java";
    FileInputStream fin;
    FileOutputStream fout;
    ObjectInputStream oin;
    ObjectOutputStream oout;
    public LessonRecord Retrieve(String name, int lesson)
        String itemFile = Path + name + ".ser";
        File f = new File(itemFile);
        LessonRecord[] r=null;
        if (f.exists() == true)
            try
                if(fin == null)
                    fin = new FileInputStream(itemFile);
                    oin = new ObjectInputStream(fin);
                r= (LessonRecord[])oin.readObject();
                System.out.println(r[lesson-1].Comment+":"+r[lesson-1].Date);
            catch(IOException ioe)
                System.out.print(ioe);
              catch(ClassNotFoundException c){
                c.printStackTrace();
            finally
                try {
                    if(fin!=null)fin.close();
                    if(oin!=null)oin.close();
                } catch (IOException ex) {
                    ex.printStackTrace();
        else
            LessonRecord LR = new LessonRecord();
            LR.Date = " ";
            LR.Comment = "File Not Found";
            return LR;
    /*create file object for Path\\Name
     *if file exists
     *  create fileinputstream
     *  create objectinputstream - oin
     *  read array of lesson records
     *  LessonRecord |r[] = oin.readObject();    need cast to array here
     *  close object input stream and file input stream
     *  return |r[lesson - 1];
     *else file does NOT EXIST
     *  LessonRecord LR = new LessonRecord();
     *  LR.date = " ";
     *  LR.comment = error message;
     *  return LR;
  return r[lesson - 1];
    public void Save(String name, String date, String comment, int lesson)
        String itemFile = Path + name + ".ser";
        File f = new File(itemFile);
        LessonRecord r[]=new LessonRecord[10];
        if (f.exists() == true)
            try
                fin = new FileInputStream(itemFile);
                oin = new ObjectInputStream(fin);
                 r = (LessonRecord[])oin.readObject();
            catch(IOException ioe)
                System.out.print(ioe);
            catch(ClassNotFoundException c){
                c.printStackTrace();
            finally
                try {
                    if(fin!=null)fin.close();
                    if(oin!=null)oin.close();
                } catch (IOException ex) {
                    ex.printStackTrace();
        else
            r = new LessonRecord[10];
   try
        r[lesson - 1] = new LessonRecord(date, comment);
        fout = new FileOutputStream(itemFile);
        oout = new ObjectOutputStream(fout);
        oout.writeObject(r);
        oout.flush();
   catch(IOException ioe)
        finally
            try {
                if(fout!=null)fout.close();
                if(oout!=null)oout.close();
            } catch (IOException ex) {
                ex.printStackTrace();
    /*create file object for Path\\Name
     *LessonRecord |r[];
     *if file exists
     *  create fileinputstream
     *  create objectinputstream - oin
     *  read array of lesson records
     *  LessonRecord |r[] = oin.readObject();    need cast to array here
     *  close object input stream and file input stream
     *else
     *  |r = new LessonRecord[10];
     *|r[lesson - 1] = new LessonRecord(date, comment);
     *createfileoutputstream(BaseDir\\Name);
     *createobjectoutputstream - oout
     *oout.write(|r);
     *closeobjectstream
     *closefilestream
}main.java and LessonRecord.java does not have any changes so you use the old code....
Thanks
Edited by: rajaram on Sep 28, 2007 1:24 PM