RFR: 8356420: Provide examples on wrapping System.in [v3]

[Naoto Sato]

On Sun, 11 May 2025 16:46:42 GMT, Alan Bateman <alanb at openjdk.org> wrote:

> 1. FileDescriptor.in: Unfortunately FileInputStream(FileDescriptor) has no overload that supports custom charsets. We should probably document both on this FD and that constructor.

The description of `FileDescriptor.in` reads:

Usually, this file descriptor is not used directly, but rather via the input stream known as System.in

And its `System.in` is hyperlinked. So I'd not add an example here.

> 2. JShell.in and JavaShellToolBuilder.in

(I assumed the first one as `JShell.Builder.in`)

These are not fields but methods to set the InputStream, so I don't think this example exercise applies to either. `jdk.jshell` package info has a code sample which uses `System.console()` instead of reading from `System.in` which is good.

> 3. A few usages in security, like password reading in sun.security.tools.keytool.Main, or javax.security.auth.callback.CallbackHandler

The former are within `sun` package which is internal, so no need for examples. The latter has code sample in the class description. In there:

new InputStreamReader(System.in)

So this one indeed need to be updated. Will address it in the next iteration.

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PR Comment: https://git.openjdk.org/jdk/pull/25155#issuecomment-2874120922