8265418: Clean-up redundant null-checks of Class.getPackageName()

[stsypanov]

As discussed in #3464 we can clean-up null-checks remaining after 8142968 as Class.getPackageName() never returns null.

---

Progress

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Issue

• JDK-8265418: Clean-up redundant null-checks of Class.getPackageName()

Reviewers

• Claes Redestad (@cl4es - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/3571/head:pull/3571
$ git checkout pull/3571

Update a local copy of the PR:
$ git checkout pull/3571
$ git pull https://git.openjdk.java.net/jdk pull/3571/head

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$ git pr checkout 3571

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https://git.openjdk.java.net/jdk/pull/3571.diff

[bridgekeeper]

👋 Welcome back stsypanov! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@stsypanov The following label will be automatically applied to this pull request:

• core-libs

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[mlbridge]

Webrevs

• 02: Full - Incremental (dc91091b)
• 01: Full (7d52a13d)
• 00: Full (b8b2ad56)

[cl4es]

Looks good to me!

[openjdk]

⚠️ @stsypanov the full name on your profile does not match the author name in this pull requests' HEAD commit. If this pull request gets integrated then the author name from this pull requests' HEAD commit will be used for the resulting commit. If you wish to push a new commit with a different author name, then please run the following commands in a local repository of your personal fork:

$ git checkout 8265418
$ git commit -c user.name='Preferred Full Name' --allow-empty -m 'Update full name'
$ git push

[openjdk]

@stsypanov 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:

8265418: Clean-up redundant null-checks of Class.getPackageName()

Reviewed-by: redestad

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 12 new commits pushed to the master branch:

• 41185d3: 8229517: Support for optional asynchronous/buffered logging
• 7c85f35: 8267123: Remove RMI Activation
• 0754266: 8267709: Investigate differences between HtmlStyle and stylesheet.css
• 23189a1: 8191786: Thread-SMR hash table size should be dynamic
• ef368b3: 8265836: OperatingSystemImpl.getCpuLoad() returns incorrect CPU load inside a container
• 10a6f5d: 8230623: Extract command-line help for -Xlint sub-options to new --help-lint
• bea4109: 8187649: ArrayIndexOutOfBoundsException in java.util.JapaneseImperialCalendar
• ec65cf8: 8240347: remove undocumented options from jlink --help message
• 3623abb: 8263087: Add a MethodHandle combinator that switches over a set of MethodHandles
• 85f6165: 8267817: [TEST] Remove unnecessary init in test/micro/org/openjdk/bench/javax/crypto/full/AESGCMBench:setup
• ... and 2 more: https://git.openjdk.java.net/jdk/compare/37bc4e2e3c2968d7419dae4f421755b6f7d06090...master

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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@cl4es) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[openjdk]

⚠️ @stsypanov the full name on your profile does not match the author name in this pull requests' HEAD commit. If this pull request gets integrated then the author name from this pull requests' HEAD commit will be used for the resulting commit. If you wish to push a new commit with a different author name, then please run the following commands in a local repository of your personal fork:

$ git checkout 8265418
$ git commit -c user.name='Preferred Full Name' --allow-empty -m 'Update full name'
$ git push

[openjdk]

@stsypanov 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:

8265418: Clean-up redundant null-checks of Class.getPackageName()

Reviewed-by: redestad

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 9 new commits pushed to the master branch:

• d9e40dd: 8199407: Skip Rebuild Remset Phase if there are no rebuild candidates
• 8dbf7aa: 8241306: Add SignatureMethodParameterSpec subclass for RSASSA-PSS params
• b14e0ee: 8265371: Change to Visual Studio 2019 16.9.3 for building on Windows at Oracle
• c887148: 8265079: Implement VarHandle invoker caching
• b64a3fb: 8265325: Optimize StubRoutines::dpow() for Math.pow(x, 0.5)
• d1c8c9e: 8197811: Test java/awt/Choice/PopupPosTest/PopupPosTest.java fails on Windows
• 7d01c98: 8265414: Variable assigned but not used in G1FreeHumongousRegionClosure
• d9e19f1: 8265226: (dc) API note in DatagramChannel.open should link to StandardProtocolFamily.UNIX
• 49b9e68: 8262165: NMT report should state how many callsites had been skipped

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.

As you do not have Committer status in this project an existing Committer must agree to sponsor your change. Possible candidates are the reviewers of this PR (@cl4es) but any other Committer may sponsor as well.

➡️ To flag this PR as ready for integration with the above commit message, type /integrate in a new comment. (Afterwards, your sponsor types /sponsor in a new comment to perform the integration).

[mlbridge]

Mailing list message from Peter Levart on core-libs-dev:

On 4/26/21 1:27 PM, ?????? ??????? wrote:

On Mon, 26 Apr 2021 08:45:52 GMT, Alan Bateman <alanb at openjdk.org> wrote:

@AlanBateman if DL is not responding, will it be ok to just revert the changes related to `java.util.concurrent`?
That should be fine, the null check in Objects.equals is benign with these usages.
One more thing I'm thinking about (not to be done in this PR of course) is to move call to `String.intern()` from where it is now in `Class.getPackageName()`

public String getPackageName() {
String pn = this.packageName;
if (pn == null) {
Class<?> c = this;
while (c.isArray()) {
c = c.getComponentType();
}
if (c.isPrimitive()) {
pn = "java.lang";
} else {
String cn = c.getName();
int dot = cn.lastIndexOf('.');
pn = (dot != -1) ? cn.substring(0, dot).intern() : ""; // <---
}
this.packageName = pn;
}
return pn;
}

to `packageName` field assignement like

this.packageName = pn.intern();

this would add two more Strings (`""` and `"java.lang"`) into string table and allow to avoid `String.equals()` in favour of `==` call when comparing package names. What do you think?

I think this is not needed as string constants are all already interned
strings (guaranteed by VM). Also be careful not to return a string which
is not interned (which would happen if you did what you are proposing
above).

Regards, Peter

[stsypanov]

Also be careful not to return a string which
is not interned (which would happen if you did what you are proposing
above).

Ok, I'm probably missing something, but when we move String.intern() call to this.packageName = pn.intern(); there is no case when non-interned String is returned: there's only one assignment to the field packageName and the value assigned is always interned, right?

[plevart]

Also be careful not to return a string which
is not interned (which would happen if you did what you are proposing
above).

Ok, I'm probably missing something, but when we move String.intern() call to this.packageName = pn.intern(); there is no case when non-interned String is returned: there's only one assignment to the field packageName and the value assigned is always interned, right?

I see:

return pn;

...in code. The local var is returned. As said, string constants are already interned. Calling .intern() on them will mean unnecessary overhead.

[stsypanov]

Oh, now I see my mistake, I believed that after pn.intern() is called variable pn can be used along with returned value. Thanks for explanation!

[bridgekeeper]

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[stsypanov]

/integrate

[openjdk]

@stsypanov
Your change (at version 7d52a13) is now ready to be sponsored by a Committer.

[cl4es]

LGTM

[stsypanov]

/integrate

[openjdk]

@stsypanov
Your change (at version dc91091) is now ready to be sponsored by a Committer.

[cl4es]

/sponsor

[openjdk]

@cl4es @stsypanov Since your change was applied there have been 12 commits pushed to the master branch:

• 41185d3: 8229517: Support for optional asynchronous/buffered logging
• 7c85f35: 8267123: Remove RMI Activation
• 0754266: 8267709: Investigate differences between HtmlStyle and stylesheet.css
• 23189a1: 8191786: Thread-SMR hash table size should be dynamic
• ef368b3: 8265836: OperatingSystemImpl.getCpuLoad() returns incorrect CPU load inside a container
• 10a6f5d: 8230623: Extract command-line help for -Xlint sub-options to new --help-lint
• bea4109: 8187649: ArrayIndexOutOfBoundsException in java.util.JapaneseImperialCalendar
• ec65cf8: 8240347: remove undocumented options from jlink --help message
• 3623abb: 8263087: Add a MethodHandle combinator that switches over a set of MethodHandles
• 85f6165: 8267817: [TEST] Remove unnecessary init in test/micro/org/openjdk/bench/javax/crypto/full/AESGCMBench:setup
• ... and 2 more: https://git.openjdk.java.net/jdk/compare/37bc4e2e3c2968d7419dae4f421755b6f7d06090...master

Your commit was automatically rebased without conflicts.

Pushed as commit ae258f1.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

[AlanBateman]

I see this has been integrated but I have concerns that the use-sites now all assume that the package name has been intern'ed. We may some crumbs, maybe in an implNote or comment in the Class::getPackageName code, otherwise we risk breakage if getPackageName changed to return a non-intern'ed string at some point.

[stsypanov]

@AlanBateman should I then add an implNote to explicitly specify that returned value must be interned?

[AlanBateman]

@AlanBateman should I then add an implNote to explicitly specify that returned value must be interned?

We need to think about this. It's we are 200% sure it will always be intern'ed then it could be specified. If we aren't sure and document it in an implNote then I've doubt that code outside of the JDK may rely on it and we'll never be able to change it.

[stsypanov]

I've looked into history and it appears, that the name of the package has been interned both in NamedPackage and Class since 8142968 where modular system was introduced