Finalising the on-ramp feature

[Brian Goetz]

This is an idea that we discussed and rejected (with extreme prejudice!) 
very early on the process.  It effectively takes every static method in 
java.lang (including what will probably seem like a random grab bag of 
things like runFinalizersOnExit) and elevates them "into the language."  
(THen, it creates a perverse incentive to put MORE stuff in java.lang 
just to get the importing.)  This is the very opposite of what we want 
to achieve here.


On 1/21/2025 10:54 AM, david Grajales wrote:
> Hi Gavin. Hope you are doing well.
> I would like to suggest a last change if allowed, hoping it's not it 
> to be not full of inconveniences.
>
> What about implicitly importing all static methods on java.lang (not 
> sure about only for compact compilation units of a general)? that 
> would make easier and shorter simple operations like parsing strings 
> to any number type, use the Math package and so on, it would be still 
> allow for Class.method() when preferred/needed without change in the 
> source code (For example if one would want to use a concrete 
> implementation of max()), I know there are some clarity issues (where 
> does this method comes from?" )besides and to be honest, it's very 
> unlikely people will use alternatives for what java lang offers in 
> most cases unless they need very specific requirements, so further 
> ambiguity is a less concern IMHO, far less disruptive in this regard 
> than star imports and import module.
>
> It's a small quality of life improvement, specially for small things 
> and students.
>
> Best regards and best wishes to all Java development team.
>
> El mar, 21 ene 2025 a la(s) 8:28 a.m., Gavin Bierman 
> (gavin.bierman at oracle.com) escribió:
>
>     Dear Experts,
>
>     With JDK 24 preparations complete, we are now planning our work
>     for JDK 25 and
>     in particular the on-ramp JEP. It is our intention to *finalise*
>     the on-ramp
>     feature in JDK 25. We are grateful for the feedback that we have
>     received from
>     our expert and developer communities - thank you! - and we have
>     been performing
>     our own extensive in-house experiments with the preview feature.
>     Given this, we
>     propose that we make the following changes/simplifications to the
>     feature when
>     it finalizes in JDK 25.
>
>     ## 1. Remove the auto-static-import feature and move the `IO` class
>
>     We had proposed that the static members of a new class `IO` would
>     automatically
>     be imported by simple compilation units. This allows the use of
>     the simple names
>     `println`, `print`, `readln`, and `read`. Whilst this is very
>     convenient, it
>     creates a bump in the on-ramp experience when migrating a simple
>     compilation
>     unit to an ordinary compilation unit, which does not implicitly
>     import these static
>     methods. This means that when migrating we either add an explicit
>     static import,
>     or rewrite all the `println`, `print`, `readln` and `read` method
>     calls to
>     qualified calls.
>
>     We have come to the conclusion that the graceful on-ramp
>     experience is the more
>     important goal. So, we propose in JDK 25 that (1) we drop the
>     automatic static
>     import of the `IO` class by simple compilation units, and (2) We
>     move the `IO`
>     class from package `java.io <http://java.io>` to `java.lang`.
>
>     This means that in simple compilation units calls to the `IO`
>     methods should be
>     qualified, i.e. `IO.println`, `IO.print`, `IO.readln` and
>     `IO.read`. However,
>     when migrating from a simple compilation unit to an ordinary
>     compilation unit,
>     no static import declaration will need to be added, nor will any
>     of these calls
>     need to be rewritten; the on-ramp experience is simpler. For example:
>
>     ```
>     // Simple.java
>     void main() {
>         IO.println("Hello, world.");
>     }
>     ```
>
>     is migrated to:
>
>     ```
>     // Ordinary.java
>     class Ordinary {
>         void main() {
>             IO.println("Hello, world.”);
>         }
>     }
>     ```
>
>
>     ## 2. Changes to the `IO` class
>
>     The new `IO` class is intended to contain the most basic
>     line-oriented I/O
>     methods for beginners.
>
>     Currently the implementation of the methods of this class are thin
>     wrappers
>     around their equivalents in the `Console` class. We propose in JDK
>     25 to
>     decouple `IO` completely from `Console` which we think will better
>     reflect the
>     expectation of developers (see, for example,
>     https://mail.openjdk.org/pipermail/amber-dev/2024-September/008933.html).
>
>     Thus we propose that `IO` printing and reading are based on
>     `System.out` and
>     `System.in`, respectively.
>
>     We do not plan to add other functionality to the `IO` class, e.g.
>     a `readInt`
>     method, in JDK 25. We observe:
>
>     1. This JEP is not the final word on improving the on-ramp
>     experience in Java,
>     but merely the first step. We can continue to work on this area in
>     future
>     JEPs.
>
>     2. I/O and data conversion are, we believe, separate concerns and,
>     as such, data
>     conversion doesn't belong in a basic I/O class. Conversion, and in
>     particular
>     the related issues around error handling, can be considered
>     separately,
>     and given the auto-import of the `java.base` module, we can easily add
>     additional utility classes in support of this in future releases.
>
>     ## 3. Revise some terminology
>
>     We're going to replace the term "simple compilation unit" with
>     "**compact**
>     compilation unit" in the spec (and replace "simple source file"
>     with "compact
>     source file" in the JEP text). Hopefully, "compact" is more
>     concrete, evocative
>     terminology (and we have used it elsewhere with records).
>
>
>     Comments welcome!
>
>     Thanks,
>     Gavin 
>
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