RFR: 8356420: Provide examples on wrapping System.in [v4]

[Naoto Sato]

On Tue, 13 May 2025 00:55:14 GMT, Stuart Marks <smarks at openjdk.org> wrote:

>> Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Reflects more comments
>
> src/java.base/share/classes/java/lang/System.java line 129:
> 
>> 127:      * within the object that handles character encoding. After this is done,
>> 128:      * subsequent reading should use only the wrapper object; operating directly
>> 129:      * on {@code System.in} results in unspecified behavior.
> 
> Sorry, I think I suggested this wording initially, but I now think it needs to be changed. I'd suggest changing the text after the semicolon to
> 
>> continuing to operate directly on {@code System.in} results in unspecified behavior.

Done.

> src/java.base/share/classes/java/util/Scanner.java line 89:
> 
>> 87:  *          String aLine = sc.nextLine();
>> 88:  *      }
>> 89:  * }
> 
> Now that I'm looking at the other examples, I have what I think is better example for using Scanner on System.in. Take this example and move it after the example below, which reads long values from the file `myNumbers`. The new example could do the same thing with the hasNextLong/nextLong loop. But instead it would read from System.in using the encoding specified by `stdin.encoding`. The example could explain that reading from files uses the default encoding (`file.encoding`) whereas reading from System.in should use `stdin.encoding` because on some systems this differs from the default encoding.

I added an extra sentence for the explanation.

> src/java.base/share/classes/javax/security/auth/callback/CallbackHandler.java line 116:
> 
>> 114:      *          System.err.flush();
>> 115:      *          nc.setName((new BufferedReader
>> 116:      *                  (new InputStreamReader(System.in, "stdin.encoding"))).readLine());
> 
> Needs to be `System.getProperty("stdin.encoding"))`.

Good catch! Thanks.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25155#discussion_r2085812565
PR Review Comment: https://git.openjdk.org/jdk/pull/25155#discussion_r2085812615
PR Review Comment: https://git.openjdk.org/jdk/pull/25155#discussion_r2085812480