Alphabetically Sort a Java Collection based upon the 'toString' value of its member items

Collections.sort(fooList,
                 new Comparator<Foo>()
                 {
                     public int compare(Foo f1, Foo f2)
                     {
                         return f1.toString().compareTo(f2.toString());
                     }        
                 });

Assuming that toString never returns null and that there are no null items in the list.

Use the API sort(List list, Comparator c)which specifies a comparator, and implement is as you wish.

Alternatively, if you do not specifically need a List, use a SortedSet, same goes with the comparator.

google-collections makes this really easy with Ordering:

Collections.sort(list, Ordering.usingToString());

Is bringing in a whole 3rd-party library just to use something you could write trivially using a Comparator (as others have provided) worthwhile? No, but google-collections is so cool you'll want to have it anyway for a bunch of other reasons.

On the sorting front, you can also easily do things like reversing:

Ordering.usingToString().reverse();

or break ties:

Ordering.usingToString().compound(someOtherComparator);

or deal with nulls:

Ordering.usingToString().nullsFirst();

etc., but there's a bunch more stuff in there (not just sorting-related, of course) that leads to really expressive code. Check it out!