/usr/lib/jvm/java-1.8-adoptium/bin/javadoc

javadoc: error - invalid flag: --help
Usage: javadoc [options] [packagenames] [sourcefiles] [@files]
  -overview <file>                 Read overview documentation from HTML file
  -public                          Show only public classes and members
  -protected                       Show protected/public classes and members (default)
  -package                         Show package/protected/public classes and members
  -private                         Show all classes and members
  -help                            Display command line options and exit
  -doclet <class>                  Generate output via alternate doclet
  -docletpath <path>               Specify where to find doclet class files
  -sourcepath <pathlist>           Specify where to find source files
  -classpath <pathlist>            Specify where to find user class files
  -cp <pathlist>                   Specify where to find user class files
  -exclude <pkglist>               Specify a list of packages to exclude
  -subpackages <subpkglist>        Specify subpackages to recursively load
  -breakiterator                   Compute first sentence with BreakIterator
  -bootclasspath <pathlist>        Override location of class files loaded
                                   by the bootstrap class loader
  -source <release>                Provide source compatibility with specified release
  -extdirs <dirlist>               Override location of installed extensions
  -verbose                         Output messages about what Javadoc is doing
  -locale <name>                   Locale to be used, e.g. en_US or en_US_WIN
  -encoding <name>                 Source file encoding name
  -quiet                           Do not display status messages
  -J<flag>                         Pass <flag> directly to the runtime system
  -X                               Print a synopsis of nonstandard options and exit

Provided by Standard doclet:
  -d <directory>                   Destination directory for output files
  -use                             Create class and package usage pages
  -version                         Include @version paragraphs
  -author                          Include @author paragraphs
  -docfilessubdirs                 Recursively copy doc-file subdirectories
  -splitindex                      Split index into one file per letter
  -windowtitle <text>              Browser window title for the documentation
  -doctitle <html-code>            Include title for the overview page
  -header <html-code>              Include header text for each page
  -footer <html-code>              Include footer text for each page
  -top    <html-code>              Include top text for each page
  -bottom <html-code>              Include bottom text for each page
  -link <url>                      Create links to javadoc output at <url>
  -linkoffline <url> <url2>        Link to docs at <url> using package list at <url2>
  -excludedocfilessubdir <name1>:.. Exclude any doc-files subdirectories with given name.
  -group <name> <p1>:<p2>..        Group specified packages together in overview page
  -nocomment                       Suppress description and tags, generate only declarations.
  -nodeprecated                    Do not include @deprecated information
  -noqualifier <name1>:<name2>:... Exclude the list of qualifiers from the output.
  -nosince                         Do not include @since information
  -notimestamp                     Do not include hidden time stamp
  -nodeprecatedlist                Do not generate deprecated list
  -notree                          Do not generate class hierarchy
  -noindex                         Do not generate index
  -nohelp                          Do not generate help link
  -nonavbar                        Do not generate navigation bar
  -serialwarn                      Generate warning about @serial tag
  -tag <name>:<locations>:<header> Specify single argument custom tags
  -taglet                          The fully qualified name of Taglet to register
  -tagletpath                      The path to Taglets
  -charset <charset>               Charset for cross-platform viewing of generated documentation.
  -helpfile <file>                 Include file that help link links to
  -linksource                      Generate source in HTML
  -sourcetab <tab length>          Specify the number of spaces each tab takes up in the source
  -keywords                        Include HTML meta tags with package, class and member info
  -stylesheetfile <path>           File to change style of the generated documentation
  -docencoding <name>              Specify the character encoding for the output
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