RFR 8030848: Collections.sort(List l, Comparator) should defer to List.sort(Comparator )

[Paul Sandoz]

Hi,

When we added the List.sort method the default implementation deferred to Collections.sort.

This is the wrong way around, since any existing use of Collections.sort say with ArrayList will not avail of the optimal implementation provided by ArrayList.sort.

To resolve this the implementation of Collections.sort can be moved to List.sort and Collections.sort can defer to List.sort.

Code changes are here:

  http://cr.openjdk.java.net/~psandoz/jdk9/JDK-8030848-Collections-sort/webrev/

I made some tweaks to Arrays.sort to preserve cases when the Comparator is null.

Existing tests provide good coverage and there are no regressions when i run j.u. tests locally.

I am not happy with the current documentation though, i think that also requires some refactoring, moving stuff from Collections.sort to List.sort and explicitly stating what the current implementation of Collections.sort does. I believe this requires no spec changes even though it may appear so. Thoughts?

Also, i am concerned that this change could cause stack overflows for list implementations that override sort and still defer to Collections.sort. Implying we should fix this for 8 or quickly in an 8u.

Paul.