RFR: 8344706: Compiler Implementation of Compact Source Files and Instance Main Methods

[Chen Liang]

On Sat, 5 Apr 2025 00:55:55 GMT, Luca Kellermann <duke at openjdk.org> wrote:

>> This is a PR that implements JEP: Compact Source Files and Instance Main Methods. Changes include:
>> - `java.io.IO` moved to `java.lang.IO`, and no longer uses `System.console()` to implement the methods (thanks to @stuart-marks)
>> - `java. ... .IO` is no longer automatically imported in any compilation unit
>> - the feature is finalized (i.e. no longer requires `--enable-preview`)
>
> src/java.base/share/classes/java/lang/IO.java line 122:
> 
>> 120:     public static void print(Object obj) {
>> 121:         System.out.print(obj);
>> 122:         System.out.flush();
> 
> Is it worth using a local variable to avoid calling `print` and `flush` on different streams in case `System.out` is reassigned in between?
> 
> 
> var out = System.out;
> out.print(obj);
> out.flush();

This code is not that perf sensitive, guess it is fine as-is

> src/java.base/share/classes/java/lang/IO.java line 147:
> 
>> 145:         } catch (IOException ioe) {
>> 146:             throw new IOError(ioe);
>> 147:         }
> 
> Was `UncheckedIOException` considered? It might be better for beginners to learn throwing exceptions instead of errors.

This implementation is not to be emulated by beginners. If an Exception.is thrown here, a user might be tempted to add handlers in their code, while this is an issue with the setup.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24438#discussion_r2029660072
PR Review Comment: https://git.openjdk.org/jdk/pull/24438#discussion_r2029659899