Consider the following case.
-----------------------------

jtools-sqe:/home/vr128054/vertest/work 428 % more s.java
public class s extends t
{
}

public class t extends x
{
}

public class x extends s
{
}

the javadoc crashes with an exception.
--------------------------------------

jtools-sqe:/home/vr128054/vertest/work 430 % javadoc s.java
Loading source file s.java...
Constructing Javadoc information...
s.java:5: class t is public, should be declared in a file named t.java
public class t extends x
       ^
s.java:9: class x is public, should be declared in a file named x.java
public class x extends s
       ^
s.java:9: cyclic inheritance involving s
public class x extends s
                       ^
Standard Doclet version 1.4 beta (04 Aug 2001)

Building tree for all the packages and classes...
javadoc: In doclet class com.sun.tools.doclets.standard.Standard, method start has thrown an exception java.lang.reflect.InvocationTargetException
java.lang.ClassCastException: com.sun.tools.javac.v8.code.Type$ErrorType
        at com.sun.tools.javadoc.ClassDocImpl.<init>(ClassDocImpl.java:111)
        at com.sun.tools.javadoc.ClassDocImpl.<init>(ClassDocImpl.java:134)
        at com.sun.tools.javadoc.DocEnv.getClassDoc(DocEnv.java:388)
        at com.sun.tools.javadoc.ClassDocImpl.superclass(ClassDocImpl.java:353)
        at com.sun.tools.doclets.ClassTree.processClass(ClassTree.java:139)
        at com.sun.tools.doclets.ClassTree.processClass(ClassTree.java:144)
        at com.sun.tools.doclets.ClassTree.processClass(ClassTree.java:144)
        at com.sun.tools.doclets.ClassTree.buildTree(ClassTree.java:108)
        at com.sun.tools.doclets.ClassTree.<init>(ClassTree.java:67)
        at com.sun.tools.doclets.standard.Standard.startGeneration(Standard.java:105)
        at com.sun.tools.doclets.standard.Standard.start(Standard.java:45)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:42)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:28)
        at java.lang.reflect.Method.invoke(Method.java:313)
        at com.sun.tools.javadoc.DocletInvoker.invoke(DocletInvoker.java:196)
        at com.sun.tools.javadoc.DocletInvoker.start(DocletInvoker.java:95)
        at com.sun.tools.javadoc.Start.parseAndExecute(Start.java:289)
        at com.sun.tools.javadoc.Start.begin(Start.java:114)
        at com.sun.tools.javadoc.Main.execute(Main.java:44)
        at com.sun.tools.javadoc.Main.main(Main.java:34)
1 error
3 warnings