On 14/03/2012 2:49 PM, Eamonn McManus wrote:
Why don't we have
public<T super E> T[] toArray(T[] a) ?
This would prevent from the cast
r[i] = (T)it.next();
It's too late to change the method signature now.
Sorry about my english, I meant why don't we have had ...
In other words, has there been a reason that it was not like that from the
beginning?
Perhaps because it is not legal Java?
Thanks Eamonn!
That's ironic. :) In "The Java Programming Language" 3rd edition,
Section 11.3 Generic Methods and Constructors, I use toArray as an
example of a generic method. I then pose the question "Shouldn't there
be some restriction between T and E as they must be compatible?", the
answer to which is "logically there could be" but "there is no way to
express this restriction. Only wildcards can be given a lower type
bound". I then continue to point out that such a restriction is not
strictly necessary as you might have a List<Object>, for example, that
you only stored Strings into, so why shouldn't you be able to pass in a
String[] to toArray? The runtime array-store checks will catch any
unsuitable array.
Cheers,
David
Éamonn
On 13 March 2012 12:16, Ulf Zibis<ulf.zi...@gmx.de> wrote:
Am 10.03.2012 13:52, schrieb David Holmes:
On 10/03/2012 12:02 PM, Ulf Zibis wrote:
Why don't we have
public<T super E> T[] toArray(T[] a) ?
This would prevent from the cast
r[i] = (T)it.next();
It's too late to change the method signature now.
Sorry about my english, I meant why don't we have had ...
In other words, has there been a reason that it was not like that from the
beginning?
Wouldn't following statement potentially throw a ClassCastException ?
r[i] = (T)it.next();
Apparently not. I passed in a String[] when it should be Object[] and got
ArrayStoreException. Checking the bytecode I don't see a checkcast.
Thanks, checking that out.
-Ulf
