A method that closely resembles a method in a super type causes javadoc to crash as follows:
java.lang.NullPointerException
at java.base/java.util.Objects.requireNonNull(Objects.java:221)
at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.Content.nullCheck(Content.java:114)
at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.markup.HtmlTree.CODE(HtmlTree.java:285)
at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.MethodWriterImpl.addOverridden(MethodWriterImpl.java:347)
at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.addMethodInfo(HtmlDocletWriter.java:296)
at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.HtmlDocletWriter.addTagsInfo(HtmlDocletWriter.java:316)
at jdk.javadoc/jdk.javadoc.internal.doclets.formats.html.MethodWriterImpl.addTags(MethodWriterImpl.java:206)
at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MethodBuilder.buildTagInfo(MethodBuilder.java:209)
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.AbstractMemberBuilder.build(AbstractMemberBuilder.java:87)
at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.buildChildren(AbstractBuilder.java:200)
at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.MethodBuilder.buildMethodDoc(MethodBuilder.java:153)
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.AbstractMemberBuilder.build(AbstractMemberBuilder.java:87)
at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.AbstractBuilder.buildChildren(AbstractBuilder.java:200)
at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildMethodDetails(ClassBuilder.java:412)
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.AbstractBuilder.buildChildren(AbstractBuilder.java:200)
at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildMemberDetails(ClassBuilder.java:346)
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.AbstractBuilder.buildChildren(AbstractBuilder.java:200)
at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.builders.ClassBuilder.buildClassDoc(ClassBuilder.java:155)
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:286)
at jdk.javadoc/jdk.javadoc.internal.doclets.toolkit.AbstractDoclet.generateClassFiles(AbstractDoclet.java:268)
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)

The test:
Date.java:
public class Date {
    /**
     * Note the return type.
     */
    public void toString() {}
}

$JAVA_HOME/bin/javadoc -d out Date.java