RFR: 8354724: Methods in java.io.Reader to read all characters and all lines [v19]

[Markus KARG]

On Wed, 14 May 2025 19:37:57 GMT, Markus KARG <duke at openjdk.org> wrote:

>> The result should be immutable and CharSequence does not provide that. 
>> The contents should not be modifiable after the method returns.
>
> A "pure" `CharSequence` *is* immutable, as it does not have mutation methods. Also, why *should* the result be immutable? If someone wants to return a `StringBuilder` for example (for whatever intent), why shouldn't he allowed to do that? In fact, it would be beneficial to return a `StringBuilder` in some cases, as it is more efficient to modify (*iff* wanted) than a `String`. It should be up to the caller and the provider of the implementation to decide about immutability; this is not the API's discretion.

> Maybe a good idea at this point if @mkarg could provide an example of server code benefitting from returning a CharSequence...

The most simple example is a file server. Incidential fact, just today I wrote a function that simply passes JSON documents received in a REST call forward to another server using another REST call (without parsing it). The document is not changed. It is *inefficient* to force it into a `String` temporarily. This is not untypical, such use cases exists often in server computing.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24728#discussion_r2089622286