ADDITIONAL SYSTEM INFORMATION :
Microsoft Windows [Version 10.0.16299.431]

A DESCRIPTION OF THE PROBLEM :
Javadoc 9 and 10 fails (pre Javadoc 9 works) when creating javadoc with

  [javadoc] java.lang.IllegalArgumentException: "F&O BASIS-WERTPAPIER-REFERENZ"
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.check(HtmlDocletWriter.java:1306)

This string value "F&O BASIS-WERTPAPIER-REFERENZ" is a constant within an inner class:

-----------------------------
public final class MyClass extends Superclass {
...
static public final class MyInnerClass {
        /** F\u0026O Basis-Wertpapier-Referenz: ISIN des Basispapiers, zu dem der Future/Option gehört ({@value}). */
        static public final String ISINUNDERLYING = "F-O BASIS-WERTPAPIER-REFERENZ"; //javadoc error workaround: remove &
-----------------------------

If I remove the "&", the exception does not occur. All files are in UTF-8. Works with pre-Java 9 versions.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
See above.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Same behaviour as in pre Java 9 versions.
ACTUAL -
  [javadoc] java.lang.IllegalArgumentException: "F&O BASIS-WERTPAPIER-REFERENZ"
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.check(HtmlDocletWriter.java:1306)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.getDocLink(HtmlDocletWriter.java:1300)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.getDocLink(HtmlDocletWriter.java:1277)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.getDocLink(HtmlDocletWriter.java:1260)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.TagletWriterImpl.valueTagOutput(TagletWriterImpl.java:409)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.taglets.ValueTaglet.getTagletOutput(ValueTaglet.java:161)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.taglets.TagletWriter.getInlineTagOutput(TagletWriter.java:274)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter$2.defaultAction(HtmlDocletWriter.java:1921)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter$2.defaultAction(HtmlDocletWriter.java:1716)
  [javadoc] at jdk.compiler/com.sun.source.util.SimpleDocTreeVisitor.visitValue(SimpleDocTreeVisitor.java:499)
  [javadoc] at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCValue.accept(DCTree.java:1050)
  [javadoc] at jdk.compiler/com.sun.source.util.SimpleDocTreeVisitor.visit(SimpleDocTreeVisitor.java:79)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.commentTagsToContent(HtmlDocletWriter.java:1930)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.addCommentTags(HtmlDocletWriter.java:1621)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.addCommentTags(HtmlDocletWriter.java:1602)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.addInlineComment(HtmlDocletWriter.java:1588)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.MethodWriterImpl.addComments(MethodWriterImpl.java:180)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MethodBuilder.buildMethodComments(MethodBuilder.java:196)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MethodBuilder.buildMethodDoc(MethodBuilder.java:152)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MethodBuilder.build(MethodBuilder.java:128)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildMethodDetails(ClassBuilder.java:393)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildMemberDetails(ClassBuilder.java:341)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildClassDoc(ClassBuilder.java:145)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.build(ClassBuilder.java:120)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDoclet.generateClassFiles(HtmlDoclet.java:267)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.generateClassFiles(AbstractDoclet.java:277)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.startGeneration(AbstractDoclet.java:211)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.run(AbstractDoclet.java:117)
  [javadoc] at jdk.javadoc/jdk.javadoc.doclet.StandardDoclet.run(StandardDoclet.java:72)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:581)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:430)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:343)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Main.execute(Main.java:63)
  [javadoc] at jdk.javadoc/jdk.javadoc.internal.tool.Main.main(Main.java:52)

CUSTOMER SUBMITTED WORKAROUND :
Use pre Java 9 or remove the "&" from the constant string.

FREQUENCY : always