Re: How to let the methods of a class only can be invoked by a special package(the class not in the package)?

From:
Jebel <Jebel.Star@gmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Fri, 25 Jan 2008 21:22:10 -0800 (PST)
Message-ID:
<7f2c3c44-8f57-4614-a758-5c574a7f92fd@s8g2000prg.googlegroups.com>
On Jan 25, 7:58 pm, Andreas Leitgeb <a...@gamma.logic.tuwien.ac.at>
wrote:

Jebel <Jebel.S...@gmail.com> wrote:

I not understand how to do this. How can I "wrap" B's methods ?
Would you please provide some code as a example?


It was based on a wrong understanding on my side. Sorry, but
I think it doesn't apply, anyway.

The point was about your class in xx.zz.gg which you could
give a such limited interface, that noone could do anything
harmful with it, even if the wrong "user" tries...

The wrapping was just meant as a way to restrict the interface:
e.g.:
package xx.zz.gg;
class B {
   // lots of public methods, some of which are potentially dangerous
   public void foo() { ... }
   public void bar() { ... }
   public void snafu() { ... }
   ...}

and:
package xx.zz.gg;
class BWrapper {
   B wrappedB;
   BWrapper(B b) { wrappedB=b; }
   private B getB() { return wrappedB; }
   // just the really important methods:
   public void foo() { do some checks, and then: getB().foo(); }}

After that, you can give all the methods of B default-access,
and no one else can use anything than foo() on B, and only through
your class BWrapper (unless they find a way to sneak code into
xx.zz or xx.zz.gg bypassing your classloader, or patching their
JVM).

Also, I don't yet understand what big evil would be unleashed by
letting people just use your xx.zz.gg.B as they feel like.


Thank you Andreas.You have teach me much, and now I understand what is
the ' wrap ' . :-)
Thank you very much.

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