RFR: 8298971: Move Console implementation into jdk internal package

[Jaikiran Pai]

On Mon, 19 Dec 2022 19:23:25 GMT, Naoto Sato <naoto at openjdk.org> wrote:

> Moving the built-in implementation of `Console` from `java.io` package into `jdk.internal.io` package. It now implements `JdkConsole` interface and is accessed through `ProxyingConsole`.

src/java.base/share/classes/jdk/internal/io/JdkConsoleImpl.java line 365:

> 363:     // For convenience
> 364:     public static JdkConsole getJdkConsole(Charset cs) {
> 365:         return INSTANCE != null ? INSTANCE : new JdkConsoleImpl().console(true, cs);

Would this singleton/caching be necessary? Or could we expect that the caller of this method would cache it (like the `java.io.Console` actually does right now)?
In theory, this current implementation in this method can potentially return an incorrect (cached) instance on a second call if the `Charset` that's passed is different from the one that was used by the cached instance that is returned. But, since we know/expect this method to be called only by the `java.io.Console` and with the same `Charset` instance, I think this is OK. I do think that if we remove the caching/singleton logic here, this class could be a bit more simpler.

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PR: https://git.openjdk.org/jdk/pull/11729