On Fri, Jan 8, 2010 at 1:37 PM, sebb <seb...@gmail.com> wrote: > On 08/01/2010, sebb <seb...@gmail.com> wrote: >> On 08/01/2010, Niall Pemberton <niall.pember...@gmail.com> wrote: >> > On Thu, Jan 7, 2010 at 9:51 PM, sebb <seb...@gmail.com> wrote: >> > > The overridable methods in DirectoryWalker currently use Collection<?> >> > > as a parameter type. >> > > >> > > As far as I can tell, the Collections need to contain File objects, so >> > > would it not be better to use Collection<File>? >> > > >> > > Might be nice to use Collection<? extends File>, but when I tried that >> > > there were some problems with the test cases. >> > > >> > > Any views? >> > >> > >> > DirectoryWalker doesn't actually control what gets put into the >> > collection - the user can put whatever they want. So someone could, >> > for example, use it to add String file names to the collection. If we >> > lock it down to File then that would break for them. >> >> >> OK, I see. Perhaps the Javadoc should make this more explicit. >> >> Also, there don't seem to be any unit tests apart from ones which use >> File entries. I'll try to add some. >> > > I'm having trouble removing the "raw type" warnings from the existing > test cases. > It's not clear how to write type-safe classes that override the > methods in DirectoryWalker. > > The override only works if one uses Collection<?> or Collection<? > extends Object> as the results parameter type, but then results.add() > generates a compiler error, as one cannot add anything to a collection > of <?>.
Yes this is not good. > One can solve the problem by casting results to the appropriate type, > but that will be an unchecked cast. Every implementation will need to > include the casts, and it does not make any use of the type-checking > features of generics. > > The DirectoryWalker class probably needs to be genericised, so the > user can specify what Collection type to be used. > > Alternatively, maybe the results parameter could be specified as > Collection<Object>. > However, that will require lots of casts in user code, and does not > make best use of generics either. > > Any other solutions? I've added a generic type to DirectoryWalker: http://svn.apache.org/viewvc?view=revision&revision=897578 Niall >> > Niall >> > >> > --------------------------------------------------------------------- >> > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org >> > For additional commands, e-mail: dev-h...@commons.apache.org >> > >> > >> > > --------------------------------------------------------------------- > To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org > For additional commands, e-mail: dev-h...@commons.apache.org > > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
