Re: Instantiation question

[kulack@xxxxxxxxxx]

> Hi Aaron, my answers are inline, tagged like this.

What does the following statement do in java:

Student show = new Student();

Student is a class that has methods that returns info like studentId.  So I
have a method named getStudentId() that returns an int.

> Allocates enough storage for an instance of the class Student.
> creates an instance of the class Student and runs
> the consturctor.
> Sets the 'show' reference to refer to the newly created instance.

In my program I reference the method getStudentId() as show.getStudentId
after I do the above instantiation.  Why do I have to do this vs. doing
something like Student.getStudentId?

> Syntactically you need to use show.getStudentId() to 'bind' or
> scope the method 'getStudentId' to the correct object instance.
>
> What if you had this:
> Assume the constructor takes the student ID.
>   Student a = new Student(4, blah, blah);
>   Student b = new Student(5, blah, blah);
>   int    id = Student.getStudentId();
> What would you expect the call to getStudentId() to return?
> 4 or 5? You can't know, because you haven't identified an
> instance for which to invoke the method on.
>
> Syntactically, Student.getStudentId() is used when the method is
> static. This means that the method is 'bound' or scoped
> to the _class_, not a particular instance.

Does my question make sense?  I didn't want to include the whole programs
as
attachments.

Aaron Bartell


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