Re: const is an overrated concept that is a source of extra typing and maintenance

From:

=?ISO-8859-1?Q?Daniel_Kr=FCgler?= <daniel.kruegler@googlemail.com>

Newsgroups:

comp.lang.c++.moderated

Date:

Thu, 25 Mar 2010 11:11:45 CST

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<6c232bde-626d-4d50-ba5b-445f5850d26d@z11g2000yqz.googlegroups.com>

On 25 Mrz., 13:27, Tonni Tielens <tonnitiel...@gmail.com> wrote:

Interesting topic. I was thinking about this a while ago. Why does
Java for instance not have a const mechanism. E.g. in Java you can say
a reference itself cannot change, but you cannot prevent someone from
modifying an objects state if he has a reference to it. Why is const
correctness never introduced in a language like Java and more
important: why do people not seem to miss it?

We are working on two applications in my team. One is a const correct C
++ application and one is a Java application. Although I understand
the idea behind const and I urge others to make const correct code, we
have never had a situation in the Java application where we thought:
"Oh, if we only had const now, this wouldn't have happened." Of course
this also goes for the construction worker who has never had a brick
falling on his head.

It is very easy to run into that problem in Java (and
we did that in one or the other occasion), but because
of the existence of this problem in Java, you use
several idioms to minimize that risk:

- Make classes immutable, e.g. String, Integer.

- Provide read-only sub-interfaces to parts of
   the class that you want to "publish".

The latter is still possible to break class invariants
unintentionally, if careless downcasting to mutable
interfaces is practiced.

Greetings from Bremen,

Daniel Kr?gler

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