FULL PRODUCT VERSION :
java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+157)
Java HotSpot(TM) 64-Bit Server VM (build 9-ea+157, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Linux pcname 4.3.0-0.bpo.1-amd64 #1 SMP Debian 4.3.5-1~bpo8+1 (2016-02-23) x86_64 GNU/Linux

A DESCRIPTION OF THE PROBLEM :
I have a wrong link tag at my javadoc like: {@link Classname<_E>}
With java 8 it appeared at the doc like text.
With java 9 at generation I got an exception

REGRESSION. Last worked in version 8u152

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Add the above specified tag to one part of the javadoc.
Generate javadoc from terminal.


ERROR MESSAGES/STACK TRACES THAT OCCUR :
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.compiler/com.sun.tools.javac.api.JavacTrees.attributeDocReference(JavacTrees.java:445)
        at jdk.compiler/com.sun.tools.javac.api.JavacTrees.getElement(JavacTrees.java:405)
        at jdk.compiler/com.sun.tools.doclint.Checker.visitReference(Checker.java:869)
        at jdk.compiler/com.sun.tools.doclint.Checker.visitReference(Checker.java:102)
        at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCReference.accept(DCTree.java:631)
        at jdk.compiler/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:71)
        at jdk.compiler/com.sun.source.util.DocTreeScanner.visitLink(DocTreeScanner.java:296)
        at jdk.compiler/com.sun.tools.doclint.Checker.visitLink(Checker.java:779)
        at jdk.compiler/com.sun.tools.doclint.Checker.visitLink(Checker.java:102)
        at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCLink.accept(DCTree.java:500)
        at jdk.compiler/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:71)
        at jdk.compiler/com.sun.source.util.DocTreeScanner.scanAndReduce(DocTreeScanner.java:83)
        at jdk.compiler/com.sun.source.util.DocTreeScanner.scan(DocTreeScanner.java:98)
        at jdk.compiler/com.sun.source.util.DocTreeScanner.visitReturn(DocTreeScanner.java:362)
        at jdk.compiler/com.sun.tools.doclint.Checker.visitReturn(Checker.java:887)
        at jdk.compiler/com.sun.tools.doclint.Checker.visitReturn(Checker.java:102)
        at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCReturn.accept(DCTree.java:654)
        at jdk.compiler/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:71)
        at jdk.compiler/com.sun.source.util.DocTreeScanner.scanAndReduce(DocTreeScanner.java:83)
        at jdk.compiler/com.sun.source.util.DocTreeScanner.scan(DocTreeScanner.java:98)
        at jdk.compiler/com.sun.source.util.DocTreeScanner.scanAndReduce(DocTreeScanner.java:106)
        at jdk.compiler/com.sun.source.util.DocTreeScanner.visitDocComment(DocTreeScanner.java:185)
        at jdk.compiler/com.sun.tools.doclint.Checker.visitDocComment(Checker.java:231)
        at jdk.compiler/com.sun.tools.doclint.Checker.visitDocComment(Checker.java:102)
        at jdk.compiler/com.sun.tools.javac.tree.DCTree$DCDocComment.accept(DCTree.java:132)
        at jdk.compiler/com.sun.source.util.DocTreePathScanner.scan(DocTreePathScanner.java:50)
        at jdk.compiler/com.sun.tools.doclint.Checker.scan(Checker.java:193)
        at jdk.compiler/com.sun.tools.doclint.DocLint.scan(DocLint.java:348)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.WorkArounds.runDocLint(WorkArounds.java:111)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.Utils.getDocCommentTree0(Utils.java:3049)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.Utils.getDocCommentTree(Utils.java:3092)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.Utils$WeakSoftHashMap.computeIfAbsent(Utils.java:3274)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.Utils.getCommentHelper(Utils.java:2882)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.VisibleMemberMap$ClassMembers.checkOnPropertiesTags(VisibleMemberMap.java:674)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.VisibleMemberMap$ClassMembers.getClassMembers(VisibleMemberMap.java:465)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.VisibleMemberMap$ClassMembers.addMembers(VisibleMemberMap.java:371)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.VisibleMemberMap$ClassMembers.mapClass(VisibleMemberMap.java:345)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.VisibleMemberMap$ClassMembers.build(VisibleMemberMap.java:340)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.VisibleMemberMap$ClassMembers.access$100(VisibleMemberMap.java:300)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.util.VisibleMemberMap.<init>(VisibleMemberMap.java:161)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MemberSummaryBuilder.<init>(MemberSummaryBuilder.java:93)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MemberSummaryBuilder.getInstance(MemberSummaryBuilder.java:111)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.BuilderFactory.getMemberSummaryBuilder(BuilderFactory.java:251)
        at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.ClassWriterImpl.getNavSummaryLinks(ClassWriterImpl.java:692)
        at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.ClassWriterImpl.addSummaryDetailLinks(ClassWriterImpl.java:677)
        at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.addNavLinks(HtmlDocletWriter.java:642)
        at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.ClassWriterImpl.getHeader(ClassWriterImpl.java:199)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildClassDoc(ClassBuilder.java:152)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:547)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.build(AbstractBuilder.java:157)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.build(ClassBuilder.java:125)
        at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDoclet.generateClassFiles(HtmlDoclet.java:263)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.generateClassFiles(AbstractDoclet.java:273)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.startGeneration(AbstractDoclet.java:207)
        at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.run(AbstractDoclet.java:117)
        at jdk.javadoc/jdk.javadoc.doclets.StandardDoclet.run(StandardDoclet.java:71)
        at jdk.javadoc/jdk.javadoc.internal.tool.Start.parseAndExecute(Start.java:604)
        at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:424)
        at jdk.javadoc/jdk.javadoc.internal.tool.Start.begin(Start.java:341)
        at jdk.javadoc/jdk.javadoc.internal.tool.Main.execute(Main.java:63)
        at jdk.javadoc/jdk.javadoc.internal.tool.Main.main(Main.java:52)

REPRODUCIBILITY :
This bug can be reproduced always.

CUSTOMER SUBMITTED WORKAROUND :
Fix the javadoc solved the problem. But I think the error message could be more usefull.