On Thu, 10 Oct 2024 17:54:51 GMT, Jan Lahoda <jlah...@openjdk.org> wrote:
>> Currently, running `java` without any parameters will lead to an output that
>> is a full `--help`, which is over 100 lines (on my computer at least), and
>> it feels overwhelming. And many people might actually want to run
>> JShell/REPL, not the `java` launcher, but it is difficult find out about
>> JShell.
>>
>> The proposal herein is to print a much shorter help, together with a pointer
>> to JShell, when the launcher does not know what to do. I.e. there is nothing
>> specified to start, and no option like `--help` is specified. In particular,
>> on my machine, it prints:
>>
>> $ java
>> openjdk 24-internal 2025-03-18
>>
>> Usage: java [options...] <what to execute> [arguments to main method...]
>>
>> Where <what to execute> is one of:
>> <MainClass> to execute the main method of a compiled class
>> -jar <jar-file.jar> to execute the main class in a JAR archive
>> -m <module>[/<MainClass>] to execute the main class of a module
>> <SourceFile.java> to compile and execute a single-file program
>>
>> Where key options include:
>> --class-path <class path>
>> a : separated list of directories and JAR archives to search for class
>> files
>> --module-path <module path>
>> a : separated list of directories and JAR archives to search for
>> modules
>>
>> For more details about this launcher: java --help
>> For an interactive Java environment: jshell
>>
>>
>> Hopefully, this may be easier both for people trying to run something, and
>> for people that are really looking for JShell.
>>
>> What do you think?
>>
>> Thanks!
>
> Jan Lahoda has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Adjusting the concise help based on review suggestions.
I've adjusted the concise help to:
$ java
openjdk 24-internal 2025-03-18
Usage: java [java options...] <application> [application arguments...]
Where <application> is one of:
<MainClass> to execute the main method of a compiled class
-jar <jar-file.jar> to execute the main class in a JAR archive
-m <module>[/<MainClass>] to execute the main class of a module
<SourceFile.java> to compile and execute a single-file program
Where key java options include:
--class-path <class path>
a ":"-separated list of directories and JAR archives to search for class
files
--module-path <module path>
a ":"-separated list of directories and JAR archives to search for modules
For more details about this launcher: java --help
For an interactive Java environment: jshell
@magicus' suggestion with `<application>` seemed good, so I used that.
Regarding the `: separated list` problem, chose `":"-separated list`, as that
is still reasonably easy to do.
Regarding "launcher" - sorry, but I don't think this is meant to refer to
launcher architecture or to multiple launchers. `java` is a launcher for Java
programs, and (to me, at least) "For more details about this launcher: java
--help" does not seem to require any very special knowledge - it is simply
about listing the options for this specific launcher.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/21411#issuecomment-2405723643
