ConcurrentModificationException from IndexWriter

I couldn't track this down to create a more minimal reproducer yet (I can still try, if this is required - I'm currently out of office, though), but with the following commands, it should be simple to reproduce the issue against the jOOQ Open Source Edition repository:


git clone https://github.com/jOOQ/jOOQ
cd jOOQ
mvn package -pl jOOQ javadoc:javadoc


This leads to the following error, which wasn't present in JDK 17, yet:


[ERROR] error: An internal exception has occurred.
[ERROR] (java.util.ConcurrentModificationException)
[ERROR] Please file a bug against the javadoc tool via the Java bug reporting page
[ERROR] (https://bugreport.java.com) after checking the Bug Database (https://bugs.java.com)
[ERROR] for duplicates. Include error messages and the following diagnostic in your report. Thank you.
[ERROR] java.util.ConcurrentModificationException
[ERROR] at java.base/java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1521)
[ERROR] at java.base/java.util.TreeMap$KeyIterator.next(TreeMap.java:1575)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.IndexWriter.addContents(IndexWriter.java:149)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.IndexWriter.generateIndexFile(IndexWriter.java:123)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.IndexWriter.generate(IndexWriter.java:91)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDoclet.generateOtherFiles(HtmlDoclet.java:278)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.startGeneration(AbstractDoclet.java:213)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.run(AbstractDoclet.java:110)
[ERROR] at jdk.javadoc/jdk.javadoc.doclet.StandardDoclet.run(StandardDoclet.java:104)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:575)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:398)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:347)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.tool.Main.execute(Main.java:57)
[ERROR] at jdk.javadoc/jdk.javadoc.internal.tool.Main.main(Main.java:46)
[ERROR] 1 error
[ERROR] 100 warnings
[ERROR] Command line was: cmd.exe /X /C ""C:\Program Files\Java\jdk-21\bin\javadoc.exe" -J-Xmx1024m @options @packages @argfile"