Diary help please.

Question

I am trying to create an appointments diary with a hashmap made up of a gregoriancalendar and an appointment in which i have a separate class for.
import jewl.*;
import java.io.*;
import java.util.Date;
import java.util.ArrayList;
import java.lang.Object;
import java.awt.*;
import java.awt.event.*;
import java.util.*;
* Write a description of class AppointmentBook here.
* @author (your name)
* @version (a version number or a date)
public class AppointmentBook
    // instance variables - replace the example below with your own
    private ListBox appMain;
    private HashMap <GregorianCalendar, Appointment> appointments;
    private String appName;
    private jewl.Frame appFrame;
    private ListBox  apptList;
    private ListBox  contactList;
    private jewl.Button   addAppt;
    private jewl.Button   deleteAppt;
    private jewl.Menu     fileMenu;
    private jewl.MenuItem newDiary;
    private jewl.MenuItem openDiary;
    private jewl.MenuItem saveDiary;
    private jewl.MenuItem saveDiaryAs;
    private jewl.MenuItem exitProgram;
    private jewl.Menu optionsMenu;
    private jewl.MenuItem addAppttt;
    private jewl.MenuItem deleteApp;
    private jewl.Button one;
    private jewl.Button two;
    private jewl.Button three;
    private jewl.Button four;
    private jewl.Button five;
    private jewl.Button six;
    private jewl.Button seven;
    private jewl.Button eight;
    private jewl.Button nine;
    private jewl.Button ten;
    private jewl.Button eleven;
    private jewl.Button twelve;
    private jewl.Button thirteen;
    private jewl.Button fourteen;
    private jewl.Button fifteen;
    private jewl.Button sixteen;
    private jewl.Button seventeen;
    private jewl.Button eighteen;
    private jewl.Button nineteen;
    private jewl.Button twenty;
    private jewl.Button tone;
    private jewl.Button ttwo;
    private jewl.Button tthree;
    private jewl.Button tfour;
    private jewl.Button tfive;
    private jewl.Button tsix;
    private jewl.Button tseven;
    private jewl.Button teight;
    private jewl.Button tnine;
    private jewl.Button thirty;
    private jewl.Button thone;
     * Constructor for objects of class AppointmentBook
    public AppointmentBook()
        // initialise instance variables
        HashMap <GregorianCalendar, Appointment> appointments = new HashMap <GregorianCalendar, Appointment>();
        appFrame  = new jewl.Frame(370,370,"Diary",'X');
        apptList = new jewl.ListBox(appFrame,5,175,340,100);
        addAppt     = new jewl.Button(appFrame,10,-30,130,25,"Add Appointment",'W');
        deleteAppt  = new jewl.Button(appFrame,150,-30,130,25,"Delete Appointment",'Y');
        fileMenu    = new jewl.Menu(appFrame,"File");
        optionsMenu = new jewl.Menu(appFrame,"Options");
        addAppttt      = new jewl.MenuItem(optionsMenu,"Add Appointment",'Z');
        deleteApp   = new jewl.MenuItem(optionsMenu,"Delete Appointment",'.');
        newDiary    = new jewl.MenuItem(fileMenu,"New",';');
        openDiary   = new jewl.MenuItem(fileMenu,"Open...",'0');
        fileMenu.addSeparator();
        saveDiary   = new jewl.MenuItem(fileMenu,"Save",'[');
        saveDiaryAs = new jewl.MenuItem(fileMenu,"Save As...",']');
        fileMenu.addSeparator();
        exitProgram = new jewl.MenuItem(fileMenu,"Exit",'/');
        one  = new jewl.Button(appFrame,5,5,50,25,"1",'1');
        two  = new jewl.Button(appFrame,60,5,50,25,"2",'2');
        three = new jewl.Button(appFrame,120,5,50,25,"3",'3');
        four  = new jewl.Button(appFrame,180,5,50,25,"4",'4');
        five = new jewl.Button(appFrame,240,5,50,25,"5",'5');
        six = new jewl.Button(appFrame,300,5,50,25,"6",'6');
        seven = new jewl.Button(appFrame,360,5,50,25,"7",'7');
        eight = new jewl.Button(appFrame,5,35,50,25,"8",'8');
        nine = new jewl.Button(appFrame,60,35,50,25,"9",'9');
        ten = new jewl.Button(appFrame,120,35,50,25,"10",'A');
        eleven = new jewl.Button(appFrame,180,35,50,25,"11",'B');
        twelve = new jewl.Button(appFrame,240,35,50,25,"12",'C');
        thirteen = new jewl.Button(appFrame,300,35,50,25,"13",'D');
        fourteen = new jewl.Button(appFrame,360,35,50,25,"14",'E');
        fifteen = new jewl.Button(appFrame,5,70,50,25,"15",'F');
        sixteen = new jewl.Button(appFrame,60,70,50,25,"16",'G');
        seventeen = new jewl.Button(appFrame,120,70,50,25,"17",'H');
        eighteen = new jewl.Button(appFrame,180,70,50,25,"18",'I');
        nineteen = new jewl.Button(appFrame,240,70,50,25,"19",'J');
        twenty = new jewl.Button(appFrame,300,70,50,25,"20",'K');
        tone = new jewl.Button(appFrame,360,70,50,25,"21",'L');
        ttwo = new jewl.Button(appFrame,5,105,50,25,"22",'M');
        tthree = new jewl.Button(appFrame,60,105,50,25,"23",'N');
        tfour = new jewl.Button(appFrame,120,105,50,25,"24",'O');
        tfive = new jewl.Button(appFrame,180,105,50,25,"25",'P');
        tsix = new jewl.Button(appFrame,240,105,50,25,"26",'Q');
        tseven = new jewl.Button(appFrame,300,105,50,25,"27",'R');
        teight = new jewl.Button(appFrame,360,105,50,25,"28",'S');
        tnine = new jewl.Button(appFrame,5,140,50,25,"29",'T');
        thirty = new jewl.Button(appFrame,60,140,50,25,"30",'U');
        thone = new jewl.Button(appFrame,120,140,50,25,"31",'V');
        newDiary.setKey('#');
        openDiary.setKey('@');
        saveDiary.setKey('~');
     * An example of a method - replace this comment with your own
     * @param  y   a sample parameter for a method
     * @return     the sum of x and y
    public void go()  throws FileNotFoundException
        while (appFrame.isValid()) {
            char c = jewl.Window.nextCommand();
            if (c == ';') {         // new diary
                newDiary();
            else if (c == '0') {    // open diary
                openDiary();
            else if (c == '[') {    // save diary
                saveDiary();
            else if (c == ']') {    // save diary as
                saveDiaryAs();
            else if (c == 'X') {    // exit
                appFrame.close();
            else if (c == 'W'){    // add appointment
                addAppt();
            else if (c == 'Y') {    // delete appointment
                deleteAppt();
            else if (c == 'Z')  {   // add appointment
                addAppt();
            else if (c == '.')  {   // delete appointment
                deleteAppt();
            else if (c == '1')  {   // delete appointment
                addAppt();
            else if (c == '2')  {   // delete appointment
                addAppt();
            else if (c == '3')  {   // delete appointment
                addAppt();
            else if (c == '4')  {   // delete appointment
                addAppt();
            else if (c == '5')  {   // delete appointment
                addAppt();
            else if (c == '6')  {   // delete appointment
                addAppt();
            else if (c == '7')  {   // delete appointment
                addAppt();
            else if (c == '8')  {   // delete appointment
                addAppt();
            else if (c == '9')  {   // delete appointment
                addAppt();
            else if (c == 'A')  {   // delete appointment
                addAppt();
            else if (c == 'B')  {   // delete appointment
                addAppt();
            else if (c == 'C')  {   // delete appointment
                addAppt();
            else if (c == 'D')  {   // delete appointment
                addAppt();
            else if (c == 'E')  {   // delete appointment
                addAppt();
            else if (c == 'F')  {   // delete appointment
                addAppt();
            else if (c == 'G')  {   // delete appointment
                addAppt();
            else if (c == 'H')  {   // delete appointment
                addAppt();
            else if (c == 'I')  {   // delete appointment
                addAppt();
            else if (c == 'J')  {   // delete appointment
                addAppt();
            else if (c == 'K')  {   // delete appointment
                addAppt();
            else if (c == 'L')  {   // delete appointment
                addAppt();
            else if (c == 'M')  {   // delete appointment
                addAppt();
            else if (c == 'N')  {   // delete appointment
                addAppt();
            else if (c == 'O')  {   // delete appointment
                addAppt();
            else if (c == 'P')  {   // delete appointment
                addAppt();
            else if (c == 'Q')  {   // delete appointment
                addAppt();
            else if (c == 'R')  {   // delete appointment
                addAppt();
            else if (c == 'S')  {   // delete appointment
                addAppt();
            else if (c == 'T')  {   // delete appointment
                addAppt();
            else if (c == 'U')  {   // delete appointment
                addAppt();
            else if (c == 'V')  {   // delete appointment
                addAppt();
    public static void start (String[] args) throws FileNotFoundException {
        AppointmentBook app = new AppointmentBook();
        app.go();
    public void refresh() {
       apptList.clear();
    public void newDiary ()
        appName = null;
        appointments.clear();
        refresh();
    public void openDiary ()
        OpenDialog d = new OpenDialog("Choose diary",'c');
        d.addFilter(".diary","Diary files");
        if (d.execute() == 'c') {
            appName = d.getName();
            try {
                FileInputStream fis = new FileInputStream(appName);
                ObjectInputStream ois = new ObjectInputStream(fis);
                appointments = (HashMap<GregorianCalendar,Appointment>)ois.readObject();
            catch (IOException e) {
                jewl.Dialog.error(e.getMessage(),"Error reading diary");
            catch (ClassNotFoundException e) {
                jewl.Dialog.error(e.getMessage(),"Error reading diary");
            refresh();
    public void saveDiary () {
        try {
            FileOutputStream fos = new FileOutputStream(appName);
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(appointments);
        catch (Exception e) {
            jewl.Dialog.error(e.getMessage(),"Error saving diary");
    public void saveDiaryAs () {
        SaveDialog d = new SaveDialog("Save diary",'s');
        d.addFilter(".diary","Diary files");
        if (d.execute() == 's') {
            appName = d.getName();
            saveDiary();
    public void addAppt () throws FileNotFoundException
        jewl.Dialog     addDialog    = new jewl.Dialog(400,200,"Enter apppointment details",'n');
        jewl.Label      dateLabel    = new jewl.Label (addDialog,10,10,80,25,"Details");
        jewl.ComboBox  month    = new jewl.ComboBox (addDialog,10,50,80,25);
        month.appendLines(new String[] {"01", "02", "03", "04", "05","06", "07", "08", "09", "10","11","12"});    
        jewl.ComboBox  day    = new jewl.ComboBox (addDialog,100,50,80,25);
        day.appendLines(new String[] {"1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23"}); 
        jewl.ComboBox  year    = new jewl.ComboBox (addDialog,190,50,80,25);
        year.appendLines(new String[] { "2007", "2008", "2009", "2010"} );
        jewl.Label      detailsLabel = new jewl.Label (addDialog,10,80,80,25,"Details");
        jewl.TextField  detailsField = new jewl.TextField (addDialog,100,80,180,25);
        jewl.Button     okButton     = new jewl.Button(addDialog,10,110,80,25,"OK",'y');
        jewl.Button     ocancelutton = new jewl.Button(addDialog,100,110,80,25,"Cancel",'n');
        if (addDialog.execute() == 'y') {
            int y = Integer.parseInt(year.getLine());
            int m = Integer.parseInt(month.getLine());
            int d = Integer.parseInt(day.getLine());
            GregorianCalendar when = new GregorianCalendar(y,m,d);
            Appointment appt = new Appointment(when,detailsField.getText());
            appointments.put(when,appt);
            refresh();
    public void deleteAppt () {
        appointments.remove(appMain.selection());
}Here is my appointment class:
import java.util.*;
import java.io.*;
public class Appointment implements Serializable {
    private GregorianCalendar   time;
    private String details;
    private int length;
     * Constructor for objects of class Appointment
    public Appointment(GregorianCalendar time, String details) {
        this(time,60,details);
    public Appointment(GregorianCalendar time, int length, String details) {
        this.time     = time;
        this.length = length;
        this.details  = details;
    public GregorianCalendar getGregorianCalendar () {
        return time;
    public String getDetails () {
        return details;
    public int getLength () {
        return length;
    public void months () {
        String[] months =  {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
}The codes compile. when a user clicks on one of the buttons, the addappt() method should add the appointment to the interface etc. however when i press "ok" i get the error java.lang.NullPointerException
     at AppointmentBook.addAppt(AppointmentBook.java:340)
     at AppointmentBook.go(AppointmentBook.java:234)
     at Open.calendarMain(Open.java:36)
with line: appointments.put(when,appt);
any help would be appreciated. thank you.

Answer 1

ive changed my appointmentbook class to this:
* A graphical user interface for an electronic appointments diary.
* @author  John English
* @version 1.0
import jewl.*;
import java.io.*;
import java.util.Date;
import java.util.ArrayList;
import java.lang.Object;
import java.awt.event.*;
import java.util.*;
public class DiaryGUI
    private HashMap<Appointment, Date> diary;
    private String   diaryName;
    private jewl.Frame    diaryFrame;
    private ListBox  apptList;
    private Button   addAppt;
    private Button   deleteAppt;
    private Menu     fileMenu;
    private MenuItem newDiary;
    private MenuItem openDiary;
    private MenuItem saveDiary;
    private MenuItem saveDiaryAs;
    private MenuItem exitProgram;
    private ComboBox month;
     * Construct an object of class DiaryGUI.
    public DiaryGUI()
        diary =     new HashMap<Appointment, Date>();
        diaryFrame  = new Frame(400,600,"CI101 appointments diary",'X');
        apptList    = new ListBox(diaryFrame,5,5,-10,-40);
        addAppt     = new Button(diaryFrame,10,-30,80,25,"Add",'A');
        deleteAppt  = new Button(diaryFrame,100,-30,80,25,"Delete",'D');
        month       = new ComboBox (diaryFrame,90,40,70,25);
        month.appendLines(new String[] {"January", "Febuary", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"});
        fileMenu    = new Menu(diaryFrame,"File");
        newDiary    = new MenuItem(fileMenu,"New",'N');
        openDiary   = new MenuItem(fileMenu,"Open...",'O');
        fileMenu.addSeparator();
        saveDiary   = new MenuItem(fileMenu,"Save",'S');
        saveDiaryAs = new MenuItem(fileMenu,"Save As...",'Z');
        exitProgram = new MenuItem(fileMenu,"Exit",'X');
        newDiary.setKey('N');
        openDiary.setKey('O');
        saveDiary.setKey('S');
     * The main program. This just creates the initial DiaryGUI object and
     * then starts it going.
    public static void main (String[] args) {
        DiaryGUI gui = new DiaryGUI();
        gui.go();
    public static void refreshCalendar(int month, int year){
        //Variables
        String[] months =  {"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
     * Process the user's interaction with the graphical user interface.
    public void go()
        while (diaryFrame.isValid()) {
            char c = Window.nextCommand();
            if (c == 'N') {         // new diary
                newDiary();
            else if (c == 'O') {    // open diary
                openDiary();
            else if (c == 'S') {    // save diary
                saveDiary();
            else if (c == 'Z') {    // save diary as
                saveDiaryAs();
            else if (c == 'X') {    // exit
                diaryFrame.close();
            else if (c == 'A') {    // add appointment
                addAppt();
            else if (c == 'D') {    // delete appointment
                deleteAppt();
    public void refresh () {
        apptList.clear();
    public void newDiary () {
        diaryName = null;
        diary.clear();
        refresh();
    public void openDiary () {
        OpenDialog d = new OpenDialog("Choose diary",'c');
        d.addFilter(".diary","Diary files");
        if (d.execute() == 'c') {
            diaryName = d.getName();
            try {
                FileInputStream fis = new FileInputStream(diaryName);
                ObjectInputStream ois = new ObjectInputStream(fis);
                diary = (HashMap<Appointment, Date>)ois.readObject();
            catch (IOException e) {
                Dialog.error(e.getMessage(),"Error reading diary");
            catch (ClassNotFoundException e) {
                Dialog.error(e.getMessage(),"Error reading diary");
            refresh();
    public void saveDiary () {
        try {
            FileOutputStream fos = new FileOutputStream(diaryName);
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(diary);
        catch (Exception e) {
            Dialog.error(e.getMessage(),"Error saving diary");
    public void saveDiaryAs () {
        SaveDialog d = new SaveDialog("Save diary",'s');
        d.addFilter(".diary","Diary files");
        if (d.execute() == 's') {
            diaryName = d.getName();
            saveDiary();
    public void addAppt () {
        Dialog     addDialog    = new Dialog(400,200,"Enter apppointment details",'n');
        Label      dateLabel    = new Label (addDialog,10,10,80,25,"Date:");
        TextField  dateField    = new TextField (addDialog,100,10,180,25);
        Label      detailsLabel = new Label (addDialog,10,40,80,25,"Details");
        TextField  durField     = new TextField (addDialog,100,10,180,25);
        Label      durLabel     = new Label (addDialog,10,40,80,25,"Details");
        TextField  detailsField = new TextField (addDialog,100,40,180,25);
        Button     okButton     = new Button(addDialog,10,70,80,25,"OK",'y');
        Button     ocancelutton = new Button(addDialog,100,70,80,25,"Cancel",'n');
        if (addDialog.execute() == 'y') {
            Date when = new Date(dateField.getText());
            Appointment appt = new Appointment(when, detailsField.getText());
            diary.put(appt,when);
            refresh();
    public void deleteAppt () {
        diary.remove(apptList.selection());
}dont know if you can help me but it lets me add an appointment but then doesnt put the appointment into the applist.
thanks again