<div dir="ltr">I guess what I'm wrestling with is that, with an implicit <font face="monospace">import module java.base,</font> now <font face="monospace">List.of</font><font face="arial, sans-serif"> means a different thing for implicit compilation units than for named ones.<br></font></div><br><div class="gmail_quote gmail_quote_container"><div dir="ltr" class="gmail_attr">On Tue, Jan 21, 2025 at 12:23 PM Brian Goetz <<a href="mailto:brian.goetz@oracle.com">brian.goetz@oracle.com</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
<div>
<font face="monospace" size="4">Consistency, and smoothing the entry
to the highway. <br>
<br>
If it's in <a href="http://java.io" target="_blank">java.io</a>, then the java.base module import picks up IO
for implicit compilation units, but not for named ones, so the
locution "IO.println" stops working without an explicit module
import, as well as all the existing Java code out there. By
putting IO in java.lang, then `IO.x` means the same thing for all
compilation units. <br>
<br>
Essentially, it is a combination of uniformity and
strength-reduction from "import-static a whole bunch of things in
implicit classes only" to "import one new class symbol, IO,
everywhere."<br>
</font><br>
<br>
<div>On 1/21/2025 12:17 PM, Ethan McCue
wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">One question I have: If the implicit <font face="monospace">import module java.base;</font><font face="arial, sans-serif"> remains, what was the impetus for
moving </font><font face="monospace">IO </font><font face="arial, sans-serif">to </font><font face="monospace">java.lang</font><font face="arial, sans-serif">?</font><br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, Jan 21, 2025 at
9:55 AM Gavin Bierman <<a href="mailto:gavin.bierman@oracle.com" target="_blank">gavin.bierman@oracle.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Dear
Experts,<br>
<br>
With JDK 24 preparations complete, we are now planning our
work for JDK 25 and<br>
in particular the on-ramp JEP. It is our intention to
*finalise* the on-ramp<br>
feature in JDK 25. We are grateful for the feedback that we
have received from<br>
our expert and developer communities - thank you! - and we
have been performing<br>
our own extensive in-house experiments with the preview
feature. Given this, we<br>
propose that we make the following changes/simplifications to
the feature when<br>
it finalizes in JDK 25. <br>
<br>
## 1. Remove the auto-static-import feature and move the `IO`
class<br>
<br>
We had proposed that the static members of a new class `IO`
would automatically<br>
be imported by simple compilation units. This allows the use
of the simple names<br>
`println`, `print`, `readln`, and `read`. Whilst this is very
convenient, it<br>
creates a bump in the on-ramp experience when migrating a
simple compilation<br>
unit to an ordinary compilation unit, which does not
implicitly import these static<br>
methods. This means that when migrating we either add an
explicit static import,<br>
or rewrite all the `println`, `print`, `readln` and `read`
method calls to<br>
qualified calls. <br>
<br>
We have come to the conclusion that the graceful on-ramp
experience is the more<br>
important goal. So, we propose in JDK 25 that (1) we drop the
automatic static<br>
import of the `IO` class by simple compilation units, and (2)
We move the `IO`<br>
class from package `<a href="http://java.io" rel="noreferrer" target="_blank">java.io</a>` to
`java.lang`. <br>
<br>
This means that in simple compilation units calls to the `IO`
methods should be<br>
qualified, i.e. `IO.println`, `IO.print`, `IO.readln` and
`IO.read`. However,<br>
when migrating from a simple compilation unit to an ordinary
compilation unit,<br>
no static import declaration will need to be added, nor will
any of these calls<br>
need to be rewritten; the on-ramp experience is simpler. For
example:<br>
<br>
```<br>
// Simple.java<br>
void main() {<br>
IO.println("Hello, world.");<br>
}<br>
```<br>
<br>
is migrated to:<br>
<br>
```<br>
// Ordinary.java<br>
class Ordinary {<br>
void main() {<br>
IO.println("Hello, world.”);<br>
}<br>
}<br>
```<br>
<br>
<br>
## 2. Changes to the `IO` class<br>
<br>
The new `IO` class is intended to contain the most basic
line-oriented I/O<br>
methods for beginners. <br>
<br>
Currently the implementation of the methods of this class are
thin wrappers<br>
around their equivalents in the `Console` class. We propose in
JDK 25 to<br>
decouple `IO` completely from `Console` which we think will
better reflect the<br>
expectation of developers (see, for example,<br>
<a href="https://mail.openjdk.org/pipermail/amber-dev/2024-September/008933.html" rel="noreferrer" target="_blank">https://mail.openjdk.org/pipermail/amber-dev/2024-September/008933.html</a>).<br>
<br>
Thus we propose that `IO` printing and reading are based on
`System.out` and<br>
`System.in`, respectively. <br>
<br>
We do not plan to add other functionality to the `IO` class,
e.g. a `readInt`<br>
method, in JDK 25. We observe:<br>
<br>
1. This JEP is not the final word on improving the on-ramp
experience in Java,<br>
but merely the first step. We can continue to work on this
area in future<br>
JEPs.<br>
<br>
2. I/O and data conversion are, we believe, separate concerns
and, as such, data<br>
conversion doesn't belong in a basic I/O class. Conversion,
and in particular<br>
the related issues around error handling, can be considered
separately,<br>
and given the auto-import of the `java.base` module, we can
easily add<br>
additional utility classes in support of this in future
releases.<br>
<br>
## 3. Revise some terminology<br>
<br>
We're going to replace the term "simple compilation unit" with
"**compact**<br>
compilation unit" in the spec (and replace "simple source
file" with "compact<br>
source file" in the JEP text). Hopefully, "compact" is more
concrete, evocative<br>
terminology (and we have used it elsewhere with records).<br>
<br>
<br>
Comments welcome!<br>
<br>
Thanks,<br>
Gavin </blockquote>
</div>
</blockquote>
<br>
</div>
</blockquote></div>