Re: Yet Another ClassCastException Question
"Timo Stamm" <firstname.lastname@example.org> wrote in message
Bjorn Abelli schrieb:
"Oliver Wong" wrote...
I thought to myself "But what if I then try to put a String into oad?"
So I tried it out, and I got a runtime ArrayStoreException. To me, this
like a pretty ugly language design.
Well, I think it's actually better with that "stricter" typesafety than
the similar construction with "generic" collections. I tested the
following snippet in 1.6:
ArrayList old = new ArrayList<Date>();
This is not a valid comparison. The compiler warns you about the usage of
the raw type in the above code. A valid complement to
Object oad = new Date;
ArrayList<Object> old = new ArrayList<Date>();
and this gives you an error.
Generics work differently than arrays, and this is going to cause confusion
now and for the rest of Java's lifetime.
Date dad = newDate
Object oad = dad;
is perfectly safe, because
oad = new Object();
will cause an ArrayStoreException then and there. No data structures will
be corrupted and no subtle bugs introduced.
On the other hand
ArrayList<Date> dal = new ArrayList<Date>();
ArrayList<Object> oal = (ArrayList<Object>)dal;
is unsafe, because
will succeed, and only at some later time will
Date d = dal.get(12);
throw an exception, making it clear that there's been a problem *somewhere*.
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