JEP proposed to target JDK 11: 330: Launch Single-File Source-Code Programs (original) (raw)

Brian Goetz brian.goetz at oracle.com
Mon May 21 15:39:12 UTC 2018

Then javac would not be a compiler for the Java Language.  You don't get to sidestep the question by saying "just hack the compiler"; either this is part of the language -- which is defined by the specification -- or it's not.

On 5/17/2018 4:55 PM, Ben Evans wrote:

What about special-casing javac to interpret #! as a single-line comment marker (synonym for //), for the first line of an input file, and nowhere else?

Thanks, Ben On Thu, May 17, 2018 at 9:50 PM, Roman Kennke <roman at kennke.org> wrote: Am 17.05.2018 um 22:12 schrieb mark.reinhold at oracle.com:

The following JEP is proposed to target JDK 11:

330: Launch Single-File Source-Code Programs http://openjdk.java.net/jeps/330 Feedback on this proposal is more than welcome, as are reasoned objections. If no such objections are raised by 23:00 UTC on Thursday, 24 May, or if they're raised and then satisfactorily answered, then per the JEP 2.0 process proposal [1] I'll target this JEP to JDK 11. - Mark

[1] http://cr.openjdk.java.net/~mr/jep/jep-2.0-02.html I like this proposal. I have a question about the shebang support though. If I write a sourcefile Test.java like this: #!/usr/bin/java public class Test { public static void main(String[] args) { System.out.println("Hello"); } } ... then it's not a valid Java source file anymore, and (currently) rejected by javac. I see that it is not relevant for the intended use because the java launcher would strip the first line (except for the newline). I still find it odd. In particular, it may end up confusing for the growing experience: - people who start learning Java using this single-source feature will find that shebang 'Java scripts' don't actually compile when passed to the Java compiler - the little Java script turns out to be 'too slow', hey, let's compile it. Oops, doesn't work. - the little Java scipt has grown to complicated and needs additional classes, but doesn't compile. - editors/IDEs might (rightly) flag it as errors etc I wonder if it might be reasonable to extend the JLS to allow for shebang support too? Or maybe even don't extend the JLS but make compilers behave nicely anyway? At the very least, there should be some language in the JEP that mentions this issue. It is a complication that seems more important than the mentioned "HelloWorld"-package with "java" classname. Best regards, Roman

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