Groups > comp.lang.java.programmer > #3861

Re: About using assertion

From	Robert Klemme <shortcutter@googlemail.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: About using assertion
Date	2011-05-09 08:24 -0700
Organization	http://groups.google.com
Message-ID	<09cb7d90-9b79-473e-9869-4476c5a0191a@w24g2000yqb.googlegroups.com> (permalink)
References	<f1e4cc83-8596-4e53-bed7-34a5209fe8c4@k3g2000prl.googlegroups.com>

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On 9 Mai, 16:36, byhesed <byhe...@gmail.com> wrote:
> I am reading a book about object-oriented design pattern.
> The book, Object-Oriented Software Development Using Java 2/e by
> Xiaoping Jia, says that...
>
> 　　　　Using assertions derived from the preconditions for all methods is
> known as defensive programming.
> 　　　　Its aim is to prevent a component from being misused.
>
> 　　　　Design Guideline: Use Assertions Aggressively
>
> 　　　　Each method should include assertions on the preconditions and
> postconditions of the method and invariants of the class
>
> Do I have to always use assertion?
> Is it better to use assertion?
>
> What's your idea?

Expressions after "assert" are only evaluated if assertions are
explicitly enabled for the class.  The idea is to be able to activate
it during testing to ensure components work as designed and have it
switched off during production in order to gain better performance
(assertion checks could be costly).

Having said that I'd say that argument checking is probably more
important than assertions.  Whether to use assertions or not depends a
lot on the nature and complexity of the class.  I also often find it
useful to have a method with boolean return value called
classInvariant() which will check a class's invariant.  You can then
call that from multiple locations (e.g. entering a method, leaving a
method).

In short: assertions are a good - when not overused.

Kind regards

robert

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Thread

About using assertion byhesed <byhesed@gmail.com> - 2011-05-09 07:36 -0700
  Re: About using assertion Robert Klemme <shortcutter@googlemail.com> - 2011-05-09 08:24 -0700
    Re: About using assertion Roedy Green <see_website@mindprod.com.invalid> - 2011-05-09 09:01 -0700
      Re: About using assertion Lew <noone@lewscanon.com> - 2011-05-09 12:11 -0400
        Re: About using assertion Robert Klemme <shortcutter@googlemail.com> - 2011-05-09 22:17 +0200
          Re: About using assertion Lew <noone@lewscanon.com> - 2011-05-09 18:49 -0400
            Re: About using assertion Robert Klemme <shortcutter@googlemail.com> - 2011-05-10 07:23 +0200
            Re: About using assertion Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2011-05-10 06:45 -0300
              Re: About using assertion Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-10 13:29 +0000
                Re: About using assertion Lew <noone@lewscanon.com> - 2011-05-10 11:21 -0400
                Re: About using assertion Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-05-10 16:01 +0000
                Re: About using assertion RedGrittyBrick <RedGrittyBrick@spamweary.invalid> - 2011-05-10 17:26 +0100
                Re: About using assertion Lew <noone@lewscanon.com> - 2011-05-10 13:25 -0400
                Re: About using assertion Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2011-05-10 21:15 +0200
          Re: About using assertion tmcd@tmcd-p4-linux.austin.tx.us (Tim McDaniel) - 2011-05-19 00:32 -0500
            Re: About using assertion Michal Kleczek <kleku75@gmail.com> - 2011-05-19 08:34 +0200
              Re: About using assertion Lew <noone@lewscanon.com> - 2011-05-19 08:46 -0400
                Re: About using assertion Michal Kleczek <kleku75@gmail.com> - 2011-05-19 15:16 +0200
                Re: About using assertion Lew <noone@lewscanon.com> - 2011-05-19 09:38 -0400
                Re: About using assertion Robert Klemme <shortcutter@googlemail.com> - 2011-05-19 07:41 -0700
                Re: About using assertion Lew <noone@lewscanon.com> - 2011-05-19 11:00 -0400
            Re: About using assertion Patricia Shanahan <pats@acm.org> - 2011-05-19 05:52 -0700
  Re: About using assertion Lew <noone@lewscanon.com> - 2011-05-09 11:35 -0400
  Re: About using assertion markspace <-@.> - 2011-05-09 11:40 -0700
    Re: About using assertion Lew <noone@lewscanon.com> - 2011-05-09 14:53 -0400

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