8305157: The java.util.Arrays class should be declared final

[minborg]

Non-instantiable utility classes should be declared final and have a private constructors.

See Effective Java, Third Edition, Joshua Bloch (for example, Item 19 or Item 22).

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change requires CSR request JDK-8305158 to be approved

Issues

• JDK-8305157: The java.util.Arrays class should be declared final
• JDK-8305158: The java.util.Arrays class should be declared final (CSR)

Reviewers

• Alan Bateman (@AlanBateman - Reviewer)
• Roger Riggs (@RogerRiggs - Reviewer)
• Brian Burkhalter (@bplb - Reviewer)

Reviewing

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[minborg]

/csr

[bridgekeeper]

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[openjdk]

@minborg an approved CSR request is already required for this pull request.

[openjdk]

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[mlbridge]

Webrevs

• 00: Full (12a9b312)

[AlanBateman]

Look fine, it can't be subclassed anyway so there is no compatibility impact.

[minborg]

Look fine, it can't be subclassed anyway so there is no compatibility impact.

I thought the change would trigger a change in the public API as the modifiers are changed for the class. This would likely be picked up by compatibility checks and so, a CSR would be needed?

[AlanBateman]

I thought the change would trigger a change in the public API as the modifiers are changed for the class. This would likely be picked up by compatibility checks and so, a CSR would be needed?

It's not a compatibility issue but a CSR is needed to track the change to the signature.

[pavelrappo]

I thought the change would trigger a change in the public API as the modifiers are changed for the class. This would likely be picked up by compatibility checks and so, a CSR would be needed?

It's not a compatibility issue but a CSR is needed to track the change to the signature.

Not that I disagree with this PR, but it would be interesting to see rationale for it in CSR.

[rgiulietti]

Would it make sense to throw an AssertionError in the constructor? Just in case...

[RogerRiggs]

The CSR implies that java.util.Arrays has a non-private constructor but it does.
The CSR should mention that the constructor is private and the Array cannot be subclassed as part of the compatibility comments.

[RogerRiggs]

Would it make sense to throw an AssertionError in the constructor? Just in case...

It hardly seems worth the bytecode; the constructor could only be invoked by breaking in using reflection and the result would be an instance with no instance methods.

[rgiulietti]

In some future, one could mistakenly instantiate the class from some new method in the class itself.
Throwing protects against such mistakes already during testing, avoiding a reviewer to purposely checking that the empty constructor is never invoked.

[jddarcy]

There are numerous examples in the JDK where we have the lone private constructor throw an exception to make sure the class isn't instantiated.

[openjdk]

@minborg This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8305157: The java.util.Arrays class should be declared final

Reviewed-by: alanb, rriggs, bpb

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 10 new commits pushed to the master branch:

• be764a7: 8302814: Delete unused CountLoopEnd instruct with CmpX
• 34f4d7f: 8304759: Add BitMap iterators
• 42df1a9: 8304991: Redundant hyphen in @param results in double-dash in javadocs
• e3855d0: 8304840: Dangling CharacterCodingException in a few javadoc descriptions
• 6727490: 8303161: [vectorapi] VectorMask.cast narrow operation returns incorrect value with SVE
• f07decb: 8272613: CharsetDecoder.decode(ByteBuffer) throws IllegalArgumentException
• 014c658: 8305086: G1 Redirty Cards phase printed twice
• 2fa0933: 8304990: unnecessary dash in @param gives double-dash in docs
• e56bcb0: 8305095: Update java/net/httpclient/CustomRequestPublisher.java to use new HttpTestServer factory methods
• 0985288: 8304681: compiler/sharedstubs/SharedStubToInterpTest.java fails after JDK-8304387

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[minborg]

/integrate

[openjdk]

Going to push as commit 9df2060.
Since your change was applied there have been 21 commits pushed to the master branch:

• b261e6c: 8304445: Remaining uses of NULL in ciInstanceKlass.cpp
• 2c38e67: 8302644: IGV: Apply filters per graph tab and not globally
• f0dba21: 8304871: Use default visibility for static library builds
• 77811fa: 8305222: Change unique_ctrl_out_or_null to unique_ctrl_out in PhaseCFG::convert_NeverBranch_to_Goto
• 2d607c9: 8262294: java/net/httpclient/ProxyAuthDisabledSchemes.java fails with HTTP/1.1 parser received no bytes
• b3ff8d1: 8303805: [REDO] JDK-8302189 and JDK-8302799
• b524a74: 8301106: Allow archived Java strings to be moved by GC
• 9643f65: 8304436: com/sun/jdi/ThreadMemoryLeakTest.java fails with "OutOfMemoryError: Java heap space" with ZGC
• 69152c3: 8305202: Fix Copyright Header in ZonedDateTimeFormatterBenchmark
• 438c969: 8304976: Optimize DateTimeFormatterBuilder.ZoneTextPrinterParser.getTree()
• ... and 11 more: https://git.openjdk.org/jdk/compare/ff368d504e9101e11c7182185f56255f429d31e3...master

Your commit was automatically rebased without conflicts.

[openjdk]

@minborg Pushed as commit 9df2060.

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