RE: Instantiation question

["Clapham, Paul" <pclapham@xxxxxxxxxxxxx>]

Well, first of all you need to declare the variable "show" to be of some
class, so the compiler knows what it is.  "show = new Student()" doesn't do
that, although you could add some "implicit declaration" to Java to say that
if "show" hasn't already been declared, then this statement declares it
implicitly.

However, there are some cases where you would want to do something like "X
vbl = new Y()".  I've done it myself.  I have several methods that produce a
List of objects.  Now, List is a (Java 2) interface that can be implemented
in different ways (ArrayList, LinkedList,...).  Usually my methods use an
ArrayList, but I might want to change that in the future.  So, I have code
like this:

public List getData(...) {
  List result = new ArrayList();
  ...
  return result;
}

Doing that minimizes the changes I'd have to make if I wanted to use a
LinkedList instead.  There are more complex situations; I've just acquired a
bunch of code that sends commands to a server over RMI, and it's loaded with
interfaces and code like that.

PC2

-----Original Message-----
From: Stone, Brad V (TC) [mailto:bvstone@taylorcorp.com]
Sent: February 7, 2001 07:57
To: 'JAVA400-L@midrange.com'
Subject: RE: Instantiation question


I'll let others answer you question, but I'd like to expand on your
question.

Why do you need to say:

Student show = new Student();

Why not just:

show = new Student();

Is there a case where you would want to do something like:

Student show = new Principal();
or
Principal show = new Student();

Maybe the answer to your original question will answer mine.  :)  I've
always thought that this type of declaration was a bit redundant.

Brad


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