RFR [15] 6394757: rev2: AbstractSet.removeAll semantics are surprisingly dependent on relative sizes

[Alan Snyder]

> On May 8, 2020, at 1:49 PM, Stuart Marks <stuart.marks at oracle.com> wrote:
> 
> The containsAll() and equals() methods both use the membership contract of the receiver, not the argument. Unfortunately, the equals() specification says,
> 
>    Returns true if the specified object is also a set, the two sets have the
>    same size, and every member of the specified set is contained in this set
>    (or equivalently, every member of this set is contained in the specified
>    set).
> 
> As should be clear from this discussion, the "equivalently" clause is incorrect -- another spec bug.

Changing Set.equals() in this way would make Set inconsistent with Object.
Do you really think that is a good idea?




Comparator<String> cc = (a, b) -> a.compareToIgnoreCase(b);

Set<String> s1 = new HashSet<>();

Set<String> s2 = new TreeSet<>(cc);

s1.add("hello");

s2.add("Hello");

s1.equals(s2) -> false

s2.equals(s1) -> true

s1.hashCode() == s2.hashCode() -> false