From gavin.bierman at oracle.com Tue Jan 21 13:28:05 2025 From: gavin.bierman at oracle.com (Gavin Bierman) Date: Tue, 21 Jan 2025 13:28:05 +0000 Subject: Finalising the on-ramp feature Message-ID: <9C5CBE70-DC9B-4A4D-85CA-7C4A94EA84FE@oracle.com> 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` 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 From brian.goetz at oracle.com Tue Jan 21 17:23:15 2025 From: brian.goetz at oracle.com (Brian Goetz) Date: Tue, 21 Jan 2025 12:23:15 -0500 Subject: Finalising the on-ramp feature In-Reply-To: References: <9C5CBE70-DC9B-4A4D-85CA-7C4A94EA84FE@oracle.com> Message-ID: Consistency, and smoothing the entry to the highway. If it's in java.io, 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. 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." On 1/21/2025 12:17 PM, Ethan McCue wrote: > One question I have: If the implicit import module java.base;?remains, > what was the impetus for moving IO to java.lang? > > On Tue, Jan 21, 2025 at 9:55?AM Gavin Bierman > wrote: > > 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 ` 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 > -------------- next part -------------- An HTML attachment was scrubbed... URL: From gavin.bierman at oracle.com Tue Jan 21 19:06:46 2025 From: gavin.bierman at oracle.com (Gavin Bierman) Date: Tue, 21 Jan 2025 19:06:46 +0000 Subject: Finalising the on-ramp feature In-Reply-To: <9C5CBE70-DC9B-4A4D-85CA-7C4A94EA84FE@oracle.com> References: <9C5CBE70-DC9B-4A4D-85CA-7C4A94EA84FE@oracle.com> Message-ID: <0AF97878-A2C7-4189-A146-57D5BC0D6005@oracle.com> [Resending with correction] # Finalising the on-ramp feature 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`, and `readln`. 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`, and `readln` 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` to `java.lang`. This means that in simple compilation units calls to the `IO` methods should be qualified, i.e. `IO.println`, `IO.print`, and `IO.readln`. 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 From gavin.bierman at oracle.com Tue Jan 21 19:07:51 2025 From: gavin.bierman at oracle.com (Gavin Bierman) Date: Tue, 21 Jan 2025 19:07:51 +0000 Subject: Finalising the on-ramp feature In-Reply-To: <9f592295-2de8-471d-82f9-6cb3e1e33026@gmail.com> References: <9C5CBE70-DC9B-4A4D-85CA-7C4A94EA84FE@oracle.com> <9f592295-2de8-471d-82f9-6cb3e1e33026@gmail.com> Message-ID: > On 21 Jan 2025, at 18:55, Cay Horstmann wrote: > > +1 > > But what is IO.read? A typo! Thanks Cay - resent with correction. Many Thanks, Gavin From forax at univ-mlv.fr Tue Jan 21 20:06:30 2025 From: forax at univ-mlv.fr (Remi Forax) Date: Tue, 21 Jan 2025 21:06:30 +0100 (CET) Subject: Finalising the on-ramp feature In-Reply-To: <0AF97878-A2C7-4189-A146-57D5BC0D6005@oracle.com> References: <9C5CBE70-DC9B-4A4D-85CA-7C4A94EA84FE@oracle.com> <0AF97878-A2C7-4189-A146-57D5BC0D6005@oracle.com> Message-ID: <1065901796.71915473.1737489990475.JavaMail.zimbra@univ-eiffel.fr> ----- Original Message ----- > From: "Gavin Bierman" > To: "amber-spec-experts" > Cc: "amber-dev" > Sent: Tuesday, January 21, 2025 8:06:46 PM > Subject: Re: Finalising the on-ramp feature > [Resending with correction] > > # Finalising the on-ramp feature > > 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. > [...] > > ## 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. yes, > > 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. yes > > ## 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). yes, > > > Comments welcome! > > Thanks, > Gavin R?mi From forax at univ-mlv.fr Tue Jan 21 20:48:07 2025 From: forax at univ-mlv.fr (Remi Forax) Date: Tue, 21 Jan 2025 21:48:07 +0100 (CET) Subject: Finalising the on-ramp feature In-Reply-To: <0AF97878-A2C7-4189-A146-57D5BC0D6005@oracle.com> References: <9C5CBE70-DC9B-4A4D-85CA-7C4A94EA84FE@oracle.com> <0AF97878-A2C7-4189-A146-57D5BC0D6005@oracle.com> Message-ID: <444088668.72101111.1737492487835.JavaMail.zimbra@univ-eiffel.fr> ----- Original Message ----- > From: "Gavin Bierman" > To: "amber-spec-experts" > Cc: "amber-dev" > Sent: Tuesday, January 21, 2025 8:06:46 PM > Subject: Re: Finalising the on-ramp feature > [Resending with correction] > > # Finalising the on-ramp feature > > 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`, and `readln`. 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`, and `readln` 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` to `java.lang`. > > This means that in simple compilation units calls to the `IO` methods should be > qualified, i.e. `IO.println`, `IO.print`, and `IO.readln`. 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.?); > } > } > ``` I am a little disapointed by this proposal, As a teacher, it means that you have to explain the dot syntax early on, which is not necessary when discovering basic things like literals, control flow, arrays, user defined functions (yes, functions not methods, because the compact class is not visible, so everything is a function). Yes, later on, when you explain the concept of IO, the dot syntax ('.'), the "println" inside "IO", the "parseInt" inside "Integer". But for the first lectures, there is no need to introduce the dot syntax. More fundamentally, this proposal is weird to me, we want to introduce compact classes so there no need to declare a container class but to print something, you have to us a syntax that says go into the container class "IO" to find the method "println". So compact class => no container class, IO.println => container class ?? I understand that it means that the migration from a compact class to an ordinary class can be seen as more complex, but it's because you are skiping an intermediary step, which is moving from the world of functions to the world of methods. I think that the world of functions is important enough so we should support it, by allowing "println" to be an alias of "IO.println" regards, R?mi