Till JDK 8, javadoc generated anchors to package descriptions. In some javadoc documentation comments in the source, there are links to package description that are broken in JDK 9 as the anchors to package description like
<a name="package.description"> is missing the package-summary.html(e.g. http://download.java.net/java/jdk9/docs/api/java/lang/package-summary.html) page.