>javadoc -help
or
>javadoc

javadoc: In doclet class com.sun.tools.doclets.standard.Standard, method optionLength has thrown an
 exception java.lang.reflect.InvocationTargetException
java.lang.NullPointerException
        at com.sun.tools.doclets.internal.toolkit.util.MessageRetriever.printNotice(MessageRetriever
.java:190)
        at com.sun.tools.doclets.internal.toolkit.util.MessageRetriever.notice(MessageRetriever.java
:386)
        at com.sun.tools.doclets.formats.html.ConfigurationImpl.optionLength(ConfigurationImpl.java:
291)
        at com.sun.tools.doclets.formats.html.HtmlDoclet.optionLength(HtmlDoclet.java:202)
        at com.sun.tools.doclets.standard.Standard.optionLength(Standard.java:12)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:324)
        at com.sun.tools.javadoc.DocletInvoker.invoke(DocletInvoker.java:209)
        at com.sun.tools.javadoc.DocletInvoker.optionLength(DocletInvoker.java:115)
        at com.sun.tools.javadoc.Start.usage(Start.java:108)
        at com.sun.tools.javadoc.Start.usageError(Start.java:400)
        at com.sun.tools.javadoc.Start.parseAndExecute(Start.java:310)
        at com.sun.tools.javadoc.Start.begin(Start.java:127)
        at com.sun.tools.javadoc.Main.execute(Main.java:41)
        at com.sun.tools.javadoc.Main.main(Main.java:31)
2 errors