On Tue, 16 Feb 2021 23:18:55 GMT, Claes Redestad <redes...@openjdk.org> wrote:
>> Modify the `unmodifiable*` methods in `java.util.Collections` to be
>> idempotent. That is, when given an immutable collection from
>> `java.util.ImmutableCollections` or `java.util.Collections`, these methods
>> will return the reference instead of creating a new immutable collection
>> that wraps the existing one.
>
> src/java.base/share/classes/java/util/Collections.java line 1130:
>
>> 1128: public static <T> Set<T> unmodifiableSet(Set<? extends T> s) {
>> 1129: if(s.getClass() == UnmodifiableSet.class ||
>> 1130: s.getClass() == ImmutableCollections.Set12.class ||
>
> These might be problematic: `ImmutableCollections.Set*` differs in behavior
> subtly from `UnmodifiableSet`, e.g., `set.contains(null)` will throw an NPE.
> I'd limit the check and optimization to `UnmodifiableSet` here
No? This unmodifiable set here just delegates call to the backing field `c`, so
all exceptions from `c`'s calls are just delegated, aren't they? The NPE will
still be thrown; it's just that the stack trace will be different (i.e. one
more level of call in the stacktrace)
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PR: https://git.openjdk.java.net/jdk/pull/2596
