JEP proposed to target JDK 11: 330: Launch Single-File Source-Code Programs (original) (raw)
Roman Kennke roman at kennke.org
Thu May 17 20:50:44 UTC 2018
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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
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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