RFR: 8270490: Charset.forName() taking fallback default value [v2]

[Naoto Sato]

On Fri, 22 Oct 2021 04:54:35 GMT, Glavo <duke at openjdk.java.net> wrote:

>> Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Moved the null sentence into @param tag.
>
> Oh, I found that I checked the outdated source code. Now this problem does not exist in `StringCoding`.
> 
> I simply browsed the latest source code of JDK and found that this idiom no longer appears outside jline. I believe that the source code of jline does not need to be modified in openjdk.
> 
> But I noticed `LauncherHelper.makePlatformString` (https://github.com/openjdk/jdk/blob/c978ca87de2d9152345dfd85983278c42bb28cd3/src/java.base/share/classes/sun/launcher/LauncherHelper.java#L887)
> 
> I don't understand why it stores `encoding` string and `isCharsetSupported` boolean values. Nor do I find references to these two fields in native code. I think it may be improved in this PR like this:
> 
> 
> 
>     private static final String encprop = "sun.jnu.encoding";
>     private static Charset charset = null;
> 
>     /*
>      * converts a c or a byte array to a platform specific string,
>      * previously implemented as a native method in the launcher.
>      */
>     static String makePlatformString(boolean printToStderr, byte[] inArray) {
>         initOutput(printToStderr);
>         if (charset == null) {
>             charset = Charset.forName(System.getProperty(encprop), Charset.defaultCharset());
>         }
>         return new String(inArray, charset);
>     }

@Glavo, thank you for the suggestions. Although applying the new method in the JDK code would be useful, I'd keep this PR just to introduce this new method.

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PR: https://git.openjdk.java.net/jdk/pull/6045