Cheers Mihai. That looks similar to what I'd done :)
James
On May 18, 5:41 pm, Mihai DINCA <mihai.di...@free.fr> wrote:
> Hi JKay
>
> You can have an int static (class level member) in the Student class
> that keeps the current count. Then a method that returns the next
> Integer, to be used in the class constructor. Something like this (it is
> not actually how I did, but it is about the same thing):
>
> public class Sudent {
> // The Student ID
> *private Integer studentID = null;*
> // The Student infos
> private StudendRecord studentDetails = null;
>
> // The constructor fills in the data about the student
> *public Student()*{
> // Increment the counter
> *this.studentID = Student.nextCounter()*;
> // Attach a StudentRecord
> this.studentDetail = new StudentRecord();
> }
>
> // The static int value keeps the current ID
> private static int *currentCounter* = 0;
> // The following method increments the counter
> private static Integer *nextCounter*(){
> return new Integer( currentCounter++ );
> }
>
> .... and so on
> }
>
> Hope it helps
> Mihai
>
> JKay a écrit :
>
>
>
>
>
> > Ok still having problems with this.
>
> > First problem - how to get studentId to increment? Can you do studentId
> > ++ for an Integer object? In the end I ended up making studentId a
> > class variable that is incremented and creating an instance variable
> > of int type called Id that holds the student's studentId. Otherwise
> > the studentId was always 3 when printed - might have just been
> > printing in the wrong order, but shouldn't you be able to assign each
> > student their own studentId?
>
> > Second problem - forgot what it was...
>
> > Have submitted the homework now, and it works, but don't feel its as
> > was intended. Could just be misinterpretation of the instructions on
> > my part though... For example:
>
> > The Student class has studentId instance variable whose type is
> > Integer type.
> > -I've made studentId a class variable and a separate instance variable
> > called Id.
>
> > On May 15, 11:05 am, "Nick Dolan" <nickdo...@gmail.com> wrote:
>
> >> Take studentercord out from settee Anna is the object and you call set on
> >> that
>
> >> e.g
> >> anna.setName("Anna");
>
> >> Nick
> >> 07961171046
>
> >> -----Original Message-----
> >> From: Mihai DINCA <mihai.di...@free.fr>
> >> Date: Sat, 15 May 2010 11:05:35
> >> To: <jkendal...@gmail.com>
>
> >> Cc: Java Programming Online Training Course By Sang
> >> Shin<javaprogrammingwithpassion@googlegroups.com>
> >> Subject: Re: [java programming] Re: Homework 1014
>
> >> I think your constructor for the class Student must do "studentRecord =
> >> new StrudentRecord()" or something like this.
>
> >> Hope it helps
> >> mihai
>
> >> JKay a écrit :
>
> >>> Tried to post the entire project here, but moderator said no.
> >>> Apparently we're not allowed to post large volumes of code, just small
> >>> snippets?
>
> >>> The project is 3 classes (StudentRecordExample.java[MAIN],
> >>> StudentRecord.java,Student.java), which have been modified from the
> >>> original MyStudentRecordExampleProject so its a bit bulky and could do
> >>> with a lot of streamlining, but I figure it should work anyways. As
> >>> said the error I'm getting is:
>
> >>> Exception in thread "main" java.lang.NullPointerException
> >>> at StudentRecordExample.main(StudentRecordExample.java:35)
> >>> Java Result: 1
>
> >>> I used the 'new' keyword to create an instance of a Student object
> >>> like so in StudentRecordExample.java:
>
> >>> Student anna = new Student();
>
> >>> Then to set the name variable for object anna of class Student, I
> >>> used:
>
> >>> anna.studentRecord.setName("Anna");
>
> >>> which as I understand it gets method setName from class studentRecord.
> >>> Do I have to explicitly link classes Student and StudentRecord some
> >>> how for this to work? BTW this line of code where I set anna's name
> >>> variable is highlighted when I click on the error, and is on line 35.
>
> >>> On May 14, 6:00 pm, Nic Fox <f...@nicfox.com> wrote:
>
> >>>> Without seeing your code it's hard to say.
>
> >>>> So you've used the 'new' keyword to make an instance of a Student
> >>>> object?
> >>>> E.g. Student anna = new Student();
>
> >>>> And then you use something like:
> >>>> anna.name = "Anna";
>
> >>>> If you've done those things then it could be an issue with variable
> >>>> scope perhaps?
>
> >>>> On 14/05/2010, at 11:47 PM, JKay wrote:
>
> >>>>> I keep getting the following error when I run my program:
>
> >>>>> Exception in thread "main" java.lang.NullPointerException
> >>>>> at StudentRecordExample.main(StudentRecordExample.java:35)
>
> >>>>> I looked up what java.lang.NullPointException is in the API and found
> >>>>> this:
>
> >>>>> "public class NullPointerException
> >>>>> extends RuntimeException
>
> >>>>> Thrown when an application attempts to use null in a case where an
> >>>>> object is required. These include:
>
> >>>>> * Calling the instance method of a null object.
> >>>>> * Accessing or modifying the field of a null object.
> >>>>> * Taking the length of null as if it were an array.
> >>>>> * Accessing or modifying the slots of null as if it were an array.
> >>>>> * Throwing null as if it were a Throwable value.
>
> >>>>> Applications should throw instances of this class to indicate other
> >>>>> illegal uses of the null object."
>
> >>>>> Which as far as I understand means that I'm trying to do something
> >>>>> with a null object. Said object is object anna of class Student, and
> >>>>> the method on the line that is throwing the exception is me attempting
> >>>>> to set the name variable for anna to "Anna"
>
> >>>>> Any ideas?
>
> >>>>> James
>
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