Cancelling appointment problems

Question

Hi:
I have written a calendar program and I have added two appointments. One appointment I have decided to cancel and I would like to remove from my list of appointments.
I written a removeApp method to remove the appointment but it does not work.(The code compiles without error and there are no runntime errors.)
Can someone help me solve this problem?
Thanks.
Describes a calendar for a set of appointments.
@version 1.0
import java.util.Vector;
import java.util.*;
public class CalendarTest
{  public static void main(String[] args)
      Calendar markCalendar = new Calendar("Mark");
      markCalendar.addApp(new Appointment("June 1","3pm","4pm", "dentist"));
       markCalendar.addApp(new Appointment("June 2","3pm","4pm", "doctor"));
      Appointment toFind = new Appointment("June 1","3pm","4pm", "dentist");
      markCalendar.removeApp(toFind);   
      markCalendar.print();
Describes a calendar for a set of appointments.
class Calendar
   Constructs a calendar for the person named.
   public Calendar(String aName)
   {  name = aName;
      appointments = new Vector();
   Adds an appointment to this Calendar.
   @param anApp The appointment to add.
   public void addApp(Appointment anApp)
      appointments.add(anApp);
   Removes an appointment from this Calendar.
   @param anApp The appointment to be removed.
   public void removeApp(Appointment toFind)
      for ( int i = 0; i < appointments.size(); i++)
         if (((Appointment)appointments.get(i)).equals(toFind))
             appointments.remove(i);// remove it;
   Prints the Calendar.
   public void print()
   {  System.out.println(name + "               C A L E N D A R");
      System.out.println();
       System.out.println("Date   Starttime    EndTime   Appointment");
      for (int i = 0; i < appointments.size(); i++)
      {  Appointment nextApp =(Appointment) appointments.get(i);
         nextApp.print();
   private Vector appointments;
   private String name;
   private Appointment theAppointment;
Describes an appointment.
class Appointment
   public Appointment(String aDate,String aStarttime,String aEndtime, String aApp)
   {  date = aDate;
      starttime = aStarttime;
       endtime = aEndtime;  
      app = aApp;
   Prints the Date, Starttime, Endtime and a description of the
   appointment.
   public void print()  
   {  System.out.println();
      System.out.println(date + "   " + starttime + "          " + endtime
          + "       " + app );
      System.out.println();
   private String date;
   private String starttime;
   private String endtime;
   private String app;

Answer 1

Warning: Long winded answer
well, here's your code:
public void removeApp(Appointment toFind)
    for ( int i = 0; i < appointments.size(); i++)
        if (((Appointment)appointments.get(i)).equals(toFind))
            appointments.remove(i);// remove it;
}I would throw in some System.out.println statements in there to let me know what Appointment I was currently looking at and whether that "if" statement ever went true, though it probably never does (I doubt there is a problem with the remove call). So, assuming that your problem is that the if statement doesn't fire when you think it should, then that means your call to the equals method isn't working out. You don't override the equals method of the Object class, so you are calling it there - here is the javadoc comments for that method:
The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any reference values x and y, this method returns true if and only if x and y refer to the same object (x==y has the value true).
So, it's no surprise that that isn't working out for you. It will only return true if the reference passed in points to the same chunk of memory that the reference in the List does.
So, you need to provide an equals method in your Appointment class that returns true if two appointments are equal. You need to provide public accessor method for your private properties of your Appointment class, so that you can provide a method like (note that you are in a better position to know what the definition of "equals" is with respect to your Appointment class):
public boolean equals(Object app) {
    if (!app.getDate().equals(this.getDate())) {
        return false;
    if (!app.getStartTime().equals(this.getStartTime()) {
        return false;
    // you get the idea
    // If you make it through all your ifs, and all is equal -
    return true;
}You might want to tweak that, depending on your idea of equals.
Lee