RFR: 8333086: Using Console.println is unnecessarily slow due to JLine initalization [v2]

[Jan Lahoda]

> Consider these two programs:
> 
> 
> public class SystemPrint {
>     public static void main(String... args) {
>         System.err.println("Hello!");
>     }
> }
> 
> and:
> 
> public class IOPrint {
>     public static void main(String... args) {
>         java.io.IO.println("Hello!");
>     }
> }
> 
> 
> They do the same conceptual thing - write a text to the output. But, `IO.println` delegates to `Console.println`, which then delegates to a `Console` backend, and the default backend is currently based on JLine.
> 
> The issues is that JLine takes a quite a long time to initialize, and in a program like this, JLine is not really needed - it is used to provide better editing experience when reading input, but there's no reading in these programs.
> 
> For example, on my computer:
> 
> $ time java -classpath /tmp SystemPrint 
> Hello!
> 
> real    0m0,035s
> user    0m0,019s
> sys     0m0,019s
> 
> $ time java -classpath /tmp --enable-preview IOPrint 
> Hello!
> 
> real    0m0,165s
> user    0m0,324s
> sys     0m0,042s
> 
> 
> The proposal herein is to delegate to the simpler `Console` backend from `java.base` as long as the user only uses methods that print to output, and switch to the JLine delegate when other methods (typically input) is used. Note that while technically `writer()` is a method doing output, it will force JLine initialization to avoid possible problems if the client caches the writer and uses it after switching the delegates.
> 
> With this patch, I can get timing like this:
> 
> $ time java --enable-preview -classpath /tmp/ IOPrint 
> Hello!
> 
> real    0m0,051s
> user    0m0,038s
> sys     0m0,020s
> 
> 
> which seems much more acceptable.
> 
> There is also #19467, which may reduce the time further.
> 
> A future work might focus on making JLine initialize faster, but avoiding JLine initialization in case where we don't need it seems like a good step to me in any case.

Jan Lahoda has updated the pull request incrementally with one additional commit since the last revision:

  Reflecting review feedback - explicitly selecting the jdk.internal.le provider in the test.

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/19479/files
  - new: https://git.openjdk.org/jdk/pull/19479/files/9886732e..7a0c448f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=19479&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=19479&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/19479.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19479/head:pull/19479

PR: https://git.openjdk.org/jdk/pull/19479