RFR: 8320971: Use BufferedInputStream.buf directly when param of implTransferTo() is trusted [v5]

[Vladimir Sitnikov]

On Fri, 8 Dec 2023 17:23:59 GMT, Markus KARG <duke at openjdk.org> wrote:

>> Sergey Tsypanov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   8320971: Use same approach as BAOS
>
> src/java.base/share/classes/java/io/OutputStream.java line 212:
> 
>> 210:      * @return true if the argument of {@link #write(byte[])}} and {@link #write(byte[], int, int)}} needn't be copied
>> 211:      */
>> 212:     boolean trusted() {
> 
> This is a strange construction. Any subclass could simply implement this as `return true;`. Where is the guard against this, and why not doing it that way?

Technically speaking, `OutputStream` is an `abstract class`, so this declaration of `boolean trusted()` is a package-protected method that will be visible and overridable only within JDK itself.
However, I agree it looks suspicious.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16879#discussion_r1420846454