Jason Tedor ac39e73183 Priority values should be unmodifiable
In Priority there is a field named values that represents an ordered, by
priority, list of all priorities. Yet, this collection is modifiable and
this collection is exposed via the public API. This means that consumers
can modify this list potentially leading to complete chaos. This commit
modifies this field so that it is unmodifiable, documents that the
returned collection is unmodifiable, and returns total order to the
world. We also punish the bad consumer here by making them make a copy
of the returned collection with which they can do as they please. This
fixes a puzzling test failure which only arises if the two tests
(PrioritizedExecutorsTests#testPriorityQueue and
PriorityTests#testCompareTo run in the same JVM, and run in the right
order).

Relates #19447
2016-07-15 08:36:59 -04:00
..