There are known javadoc errors (e.g. mismatch between @param and parameter names) in core jdk non-public API. An attempt to find all such (is there some better/blessed way?) via:

--- a/make/Javadoc.gmk
+++ b/make/Javadoc.gmk
@@ -186,7 +186,7 @@
     #
 
 DEFAULT_JAVADOC_OPTIONS := -XDignore.symbol.file=true -use -keywords -notimestamp \
- -serialwarn -encoding ISO-8859-1 -breakiterator --system none
+ -serialwarn -encoding ISO-8859-1 -breakiterator --system none -package
 
 ################################################################################
 # Setup make rules for running javadoc.

provokes a javadoc internal error:

 $ rm -rf ./build/linux-x86_64-normal-server-release/images/docs/api; make docs-javadoc
...
Building target 'docs-javadoc' in configuration 'linux-x86_64-normal-server-release'
Generating Javadoc from 224 package(s) for api
javadoc: error - An internal exception has occurred.
(java.lang.NullPointerException)
Please file a bug against the javadoc tool via the Java bug reporting page
(http://bugreport.java.com) after checking the Bug Database (http://bugs.java.com)
for duplicates. Include error messages and the following diagnostic in your report. Thank you.
java.lang.NullPointerException
at jdk.javadoc.internal.doclets.toolkit.util.JavaScriptScanner.visitAttribute(JavaScriptScanner.java:98)
at jdk.javadoc.internal.doclets.toolkit.util.JavaScriptScanner.visitAttribute(JavaScriptScanner.java:46)
at com.sun.tools.javac.tree.DCTree$DCAttribute.accept(DCTree.java:190)
at com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:71)
at com.sun.source.util.DocTreeScanner.scan(DocTreeScanner.java:98)
at com.sun.source.util.DocTreeScanner.visitStartElement(DocTreeScanner.java:437)
at jdk.javadoc.internal.doclets.toolkit.util.JavaScriptScanner.visitStartElement(JavaScriptScanner.java:57)
at jdk.javadoc.internal.doclets.toolkit.util.JavaScriptScanner.visitStartElement(JavaScriptScanner.java:46)
at com.sun.tools.javac.tree.DCTree$DCStartElement.accept(DCTree.java:810)
at com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:71)
at com.sun.source.util.DocTreeScanner.scanAndReduce(DocTreeScanner.java:83)
at com.sun.source.util.DocTreeScanner.scan(DocTreeScanner.java:98)
at com.sun.source.util.DocTreeScanner.scanAndReduce(DocTreeScanner.java:106)
at com.sun.source.util.DocTreeScanner.visitDocComment(DocTreeScanner.java:184)
at com.sun.tools.javac.tree.DCTree$DCDocComment.accept(DCTree.java:132)
at com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:50)
at jdk.javadoc.internal.doclets.toolkit.util.JavaScriptScanner.scan(JavaScriptScanner.java:49)
at jdk.javadoc.internal.doclets.toolkit.util.Utils.getDocCommentTree0(Utils.java:3037)
at jdk.javadoc.internal.doclets.toolkit.util.Utils.getDocCommentTree(Utils.java:3088)
at jdk.javadoc.internal.doclets.toolkit.util.Utils$WeakSoftHashMap.computeIfAbsent(Utils.java:3270)
at jdk.javadoc.internal.doclets.toolkit.util.Utils.getCommentHelper(Utils.java:2878)
at jdk.javadoc.internal.doclets.toolkit.util.Utils.hasBlockTag(Utils.java:2960)
at jdk.javadoc.internal.doclets.toolkit.util.Utils.hasBlockTag(Utils.java:2956)
at jdk.javadoc.internal.doclets.toolkit.util.Utils.isHidden(Utils.java:1556)
at jdk.javadoc.internal.doclets.toolkit.util.ClassTree.buildTree(ClassTree.java:177)
at jdk.javadoc.internal.doclets.toolkit.util.ClassTree.<init>(ClassTree.java:120)
at jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.startGeneration(AbstractDoclet.java:205)
at jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.run(AbstractDoclet.java:117)
at jdk.javadoc.doclet.StandardDoclet.run(StandardDoclet.java:68)
at jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:608)
at jdk.javadoc.internal.tool.Start.begin(Start.java:424)
at jdk.javadoc.internal.tool.Start.begin(Start.java:341)
at jdk.javadoc.internal.tool.Main.execute(Main.java:63)
at jdk.javadoc.internal.tool.Main.main(Main.java:52)
1 error