Unlike most other tools, running `javadoc` without any arguments does not show you how to use the tool or point you to use the `--help` option, this can be improved.

```
W $ ./java
Usage: java [java options...] <application> [application arguments...]

Where <application> is one of:
  <mainclass> to execute the main method of a compiled main class
  -jar <jarfile>.jar to execute the main class of a JAR archive
  -m <module>[/<mainclass>] to execute the main class of a module
  <sourcefile>.java to compile and execute a source-file program

Where key java options include:
  --class-path <class path>
    where <class path> is a list of directories and JAR archives to search for class files, separated by ":"
  --module-path <module path>
    where <module path> is a list of directories and JAR archives to search for modules, separated by ":"
  -version
    to print product version to the error stream and exit

For additional help on usage: java --help
For an interactive Java environment: jshell
W $ ./jar
Usage: jar [OPTION...] [ [--release VERSION] [-C dir] files] ...
Try `jar --help' for more information.
W $ ./jpackage
Usage: jpackage <options>
Use jpackage --help (or -h) for a list of possible options
W $ javadoc
error: No modules, packages or classes specified.
1 error
```