RFR: 8301120: Cleanup utility classes java.util.Arrays and java.util.Collections [v2]

[Stuart Marks]

On Wed, 25 Jan 2023 22:23:26 GMT, Tagir F. Valeev <tvaleev at openjdk.org> wrote:

>> number of minor cleanups could be done in Arrays and Collections utility classes.
>> In Arrays:
>> - Redundant import jdk.internal.misc.Unsafe;
>> - C-style array declaration is used in public static boolean equals(short[] a, short a2[]) (that's the only place in the whole file)
>> 
>> In Collections:
>> - A few obsolete "unchecked" and "rawtypes" suppressions
>> - Unnecessary local variable initializer in get() method
>> - Raw type can be avoided in a number of casts
>> - Explicit type parameters could be omitted or converted to diamonds
>> - A couple of javadoc links on private APIs are malformed
>
> Tagir F. Valeev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Revert cast removal

Overall looks good, no changes necessary, comments are just observations.

I'll come back and approve this when my CI build finishes.

src/java.base/share/classes/java/util/Collections.java line 1636:

> 1634:             @SuppressWarnings({"unchecked"})
> 1635:             UnmodifiableEntrySet(Set<? extends Map.Entry<? extends K, ? extends V>> s) {
> 1636:                 super((Set<Map.Entry<K, V>>)s);

Huh, good catch, there doesn't appear to be a "limitation in the type system" here, either currently or in older versions of javac going back to JDK 7.

src/java.base/share/classes/java/util/Collections.java line 5428:

> 5426:             return (o == this) ||
> 5427:                 (o instanceof ReverseComparator2<?> that &&
> 5428:                  cmp.equals(that.cmp));

Nice, using an instanceof pattern where we had missed it previously.

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PR: https://git.openjdk.org/jdk/pull/12207