Question

Im making a contact list, and my code compiles and runs, when you add the contact, type or email or phone its supposed to read them to you, the problem I have here is when I add the contacts and press next or previous, first or last it doesnt read the Name Contact, but it reads everything else…does it have to do something with spacing ? here is what I have…thanks

import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;



 public class ContactSystem extends JFrame{
//Specify the size of five string fields in the record
final static int NAME_SIZE = 32;
final static int TYPE_SIZE = 32;
final static int CITY_SIZE = 20;
final static int PHONE_SIZE = 15;
final static int EMAIL_SIZE = 15;
final static int RECORD_SIZE =
        (NAME_SIZE + TYPE_SIZE + CITY_SIZE + PHONE_SIZE + EMAIL_SIZE);

//access contact.dat using RandomAccessFile
private RandomAccessFile raf;

//Text Fields
private JTextField jbtName = new JTextField(NAME_SIZE);
private JTextField jbtType = new JTextField(TYPE_SIZE);
private JTextField jbtCity = new JTextField(CITY_SIZE);
private JTextField jbtPhone = new JTextField(PHONE_SIZE);
private JTextField jbtEmail = new JTextField(EMAIL_SIZE);

//Buttons
private JButton jbtAdd = new JButton("Add");
private JButton jbtFirst = new JButton("First");
private JButton jbtNext = new JButton("Next");
private JButton jbtPrevious = new JButton("Previous");
private JButton jbtLast = new JButton("Last");

public ContactSystem(){
    //open or create a random access file

    try {
        raf = new RandomAccessFile("contact.txt", "rw");
    }
    catch(IOException ex) {
        System.out.print("Error: " + ex);
        System.exit(0);
    }

    //Panel p1 for holding labels Name , Type, Email or phone
    JPanel p1 = new JPanel();
    p1.setLayout(new GridLayout(3,1));
    p1.add(new JLabel("Name Contact"));
    p1.add(new JLabel("Email Address"));
    p1.add(new JLabel("Type of Contact"));

    //Panel jpPhone for holding Phone
    JPanel jpPhone = new JPanel();
    jpPhone.setLayout(new BorderLayout());
    jpPhone.add(new JLabel("Phone"), BorderLayout.WEST);
    jpPhone.add(jbtPhone, BorderLayout.CENTER);

    //Panel jpEmail for holding Phone
    JPanel jpEmail = new JPanel();
    jpEmail.setLayout(new BorderLayout());
    jpEmail.add(new JLabel("Phone"), BorderLayout.WEST);
    jpEmail.add(jbtEmail, BorderLayout.CENTER);

    // Panel p2 for holding jpPhone and jpEmail
    JPanel p2 = new JPanel();
    p2.setLayout(new BorderLayout());
    p2.add(jpPhone, BorderLayout.WEST);
    p2.add(jpPhone, BorderLayout.CENTER);

    JPanel p3 = new JPanel();
    p3.setLayout(new BorderLayout());
    p3.add(jbtCity, BorderLayout.CENTER);
    p3.add(p2, BorderLayout.EAST);

    //panel p4 for holding jtfName, jtfType, and p3
    JPanel p4 = new JPanel();
    p4.setLayout(new GridLayout(3,1));
    p4.add(jbtName);
    p4.add(jbtType);
    p4.add(p3);

    //place p1 and p4 into jpContact
    JPanel jpContact = new JPanel(new BorderLayout());
    jpContact.add(p1, BorderLayout.WEST);
    jpContact.add(p4, BorderLayout.CENTER);

    //set panel with line border
    jpContact.setBorder(new BevelBorder(BevelBorder.RAISED));

    //add buttons to a panel
    JPanel jpButton = new JPanel();
    jpButton.add(jbtAdd);
    jpButton.add(jbtFirst);
    jpButton.add(jbtNext);
    jpButton.add(jbtPrevious);
    jpButton.add(jbtLast);

    //add jpContact and jpButton to the frame

    add(jpContact, BorderLayout.CENTER);
    add(jpButton, BorderLayout.SOUTH);

    jbtAdd.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            writeContact();

        }
    });
    jbtFirst.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            try {
                if (raf.length() > 0) readContact(0);
            }
            catch(IOException ex){
                ex.printStackTrace();
            }
        }
    });
    jbtNext.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e) {
            try {
                long currentPosition = raf.getFilePointer();
                if (currentPosition < raf.length())
                    readContact(currentPosition);

            }
            catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    });

    jbtPrevious.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            try {
                long currentPosition = raf.getFilePointer();
                if(currentPosition - 2 * RECORD_SIZE > 0)
                    //why 2 * 2 * RECORD_SIZE? see the the follow-up remarks
                    readContact(currentPosition - 2 * 2 * RECORD_SIZE);
                else
                    readContact(0);

            }
            catch(IOException ex){
                ex.printStackTrace();
            }
        }
    });

    jbtLast.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent e) {
            try {
                long lastPosition = raf.length();
                if(lastPosition > 0)
                    //why 2 * RECORD_SIZE? see the follow up remarks
                    readContact(lastPosition - 2 * RECORD_SIZE);

            }
            catch (IOException ex) {
                ex.printStackTrace();
            }
        }
    });

    try {
        if (raf.length() > 0) readContact(0);

    }

    catch (IOException ex) {
        ex.printStackTrace();

    }


}

//write a record at the end of file

public void writeContact() {

    try {
        raf.seek(raf.length());
        FixedLengthStringIO.writeFixedLengthString(
                jbtName.getText(), NAME_SIZE, raf);
        FixedLengthStringIO.writeFixedLengthString(
                jbtType.getText(), TYPE_SIZE, raf);
        FixedLengthStringIO.writeFixedLengthString(
                jbtCity.getText(), CITY_SIZE, raf);
        FixedLengthStringIO.writeFixedLengthString(
                jbtPhone.getText(), PHONE_SIZE, raf);
        FixedLengthStringIO.writeFixedLengthString(
                jbtEmail.getText(), EMAIL_SIZE, raf);

    }
    catch (IOException ex) {
        ex.printStackTrace();
    }
}

//read a contact at the specific position
public void readContact(long position) throws IOException{
    raf.seek(position);
    String name = FixedLengthStringIO.readFixedLengthString(
            NAME_SIZE, raf);
    String type = FixedLengthStringIO.readFixedLengthString(
            TYPE_SIZE, raf);
    String city = FixedLengthStringIO.readFixedLengthString(
            CITY_SIZE, raf);
    String phone = FixedLengthStringIO.readFixedLengthString(
            PHONE_SIZE, raf);
    String email = FixedLengthStringIO.readFixedLengthString(
            EMAIL_SIZE, raf);

    jbtName.setText(name);
    jbtType.setText(type);
    jbtCity.setText(city);
    jbtName.setText(phone);
    jbtName.setText(email);

}



/**
 * @param args
 */
public static void main(String[] args) {
    // TODO Auto-generated method stub

    ContactSystem frame = new ContactSystem();
    frame.pack();
    frame.setTitle("Contact System");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setVisible(true);

}

}

fixedlengthstringIO class

  import java.io.*;


  public class FixedLengthStringIO {

//read fixed number of characters from datainput stream
public static String readFixedLengthString(int size,
        DataInput in) throws IOException {
    //declare an array of characters
    char[] chars = new char[size];

    //read fixed number of characters to the array
    for(int i = 0; i < size; i++)
        chars[i] = in.readChar();
    return new String (chars);
}

//write fixed number of characters to a dataoutput stream

public static void writeFixedLengthString(String s, int size,
        DataOutput out) throws IOException {
    char[] chars = new char[size];

    //fill an array of characters from the string
    s.getChars(0, Math.min(s.length(), size), chars, 0);

    //fill in blank characters in the rest of the array
    for (int i = Math.min(s.length(), size); i < chars.length; i++)
        chars[i] = ' ';

    //create and write a new string padded with blank characters
    out.writeChars(new String(chars));
}
}

here is when I type in contact name, type, email etc into the list

and when I press next or previous, or first or last, it doesnt read the name..

Answer 1

Glitch is in your readContact method, change this

 public void readContact(long position) throws IOException {
        raf.seek(position);
        String name = FixedLengthStringIO.readFixedLengthString(
                NAME_SIZE, raf);
        String type = FixedLengthStringIO.readFixedLengthString(
                TYPE_SIZE, raf);
        String city = FixedLengthStringIO.readFixedLengthString(
                CITY_SIZE, raf);
        String phone = FixedLengthStringIO.readFixedLengthString(
                PHONE_SIZE, raf);
        String email = FixedLengthStringIO.readFixedLengthString(
                EMAIL_SIZE, raf);

        jbtName.setText(name);
        jbtType.setText(type);
        jbtCity.setText(city);
        jbtPhone.setText(phone);
        jbtEmail.setText(email);

    }

Also instead of adding separate ActionListner command button you can implement like

public class ContactSystem extends JFrame implements ActionListener 
{
  .....
  jbtAdd.addActionListener(this);
  jbtFirst.addActionListener(this);
  .....

  @Override
  public void actionPerformed(ActionEvent e) {
    String actionCommand = e.getActionCommand();
    if(actionCommand.equals("Add")) {
        //do add stuff
    } else if (actionCommand.equals("First")) {
        // move first
    }
  }
}