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Re: the benefits of immutability

Seth Gordon <sethg@ropine.com> writes:
> On Mon, 2003-08-18 at 08:50, Vadim Nasardinov wrote:
> > The problem is not that you can't add methods safely.  The problem is
> > that it is too easy to add them unsafely  One of the String's stated
> > invariants is its guaranteed immutability.  The only way to make sure
> > this invariant is *never* violated is to prevent subclassing.  Thus,
> > true immutability also requires finality.
> Object.equals() has a number of stated invariants, too (e.g.,
> transitivity), but they're documented, anyone who overloads the method
> is responsible for following those invariants.  Why can't the
> immutability of String objects be handled the same way?

His so-called "reason" doesn't explain why StringBuffer is final, too,
in any case.

Perry E. Metzger		perry@piermont.com