Re: Question about calling constructors of inner classes across different packages

From:
Daniele Futtorovic <da.futt.newsLOVELYSPAM@laposte.net>
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 04 Feb 2008 00:37:34 +0100
Message-ID:
<fo5j6f$umo$1@aioe.org>
On 2008-02-03 08:59 +0100, Dural allegedly wrote:

Here's my scenario: I have an interface, a class with an inner class
 that implements the interface, and a second class that extends the
first class (and the inner class as well, since I've made it
protected.) The interface, base class, and derived class are all in
separate packages.

Here are my interfaces and classes: Interface I, base class A, inner
 class AI (extends interface I), derived class B:

-------------------------------------------------------------------------------------
 package testbed.subpacka;

public interface I { void f(); }

--------------------------------------------------------------------------------------
 package testbed.subpackb;

import testbed.subpacka.*;

public class A {

protected class AI implements I { public AI() { // Remove public
and B (below) won't compile System.out.println("AI constructed"); }
public void f() { System.out.println("AI.f()"); } } }
-----------------------------------------------------------------------------------
 package innerclasses;

import testbed.subpacka.*; import testbed.subpackb.*;

public class B extends A { // Inner class AI and function f()
inherited from A

public I g() { return new AI(); } public static void main(String[]
args) { B b= new B(); I t = b.g(); t.f(); } }

------------------------------------------------------------------------------
 Again, note the different packages, as that's what leads to the
issue at hand:

My problem lies with the B.g() method. Unless I make a AI's
constructor public, B can't return a new AI() in the g() method. I
don't want to make AI's constructor public if I can avoid it.

It seems odd that a class can inherit a protected inner class from a
base class, yet be unable to create a new instance of the inner class
 unless the constructor is public, merely because the base and
derived classes are in different packages. Is there a simple way
around this problem?

Thanks for any feedback -


It doesn't really matter for the c'tor to be public. The c'tor will only
be visible to code to whom the class is visible too.
If you want finer control over the accessibility, using a factory method
like Daniel suggested would be the way to go.

DF.

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