On 09/01/2010, Niall Pemberton <niall.pember...@gmail.com> wrote: > 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 >
Great. I've added a String Collection test to the generics test case. Shall I add it to the Java4 version? > 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 > > --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
