RFR: 8341566: Adding factory for non-synchronized CharSequence Reader [v3]

[Alan Bateman]

On Sun, 6 Oct 2024 17:44:53 GMT, Markus KARG <duke at openjdk.org> wrote:

>> This Pull Requests proposes an implementation for [JDK-8341566](https://bugs.openjdk.org/browse/JDK-8341566): Adding the new method `public static Reader Reader.of(CharSequence)` will return an anonymous, non-synchronized implementation of a `Reader` for each kind of `CharSequence` implementation. It is optimized for `String`, `StringBuilder`, `StringBuffer` and `CharBuffer`.
>> 
>> In addition, this Pull Request proposes to replace the implementation of `StringReader` to become a simple synchronized wrapper around `Reader.of(CharSequence)` for the case of `String` sources. To ensure correctness, this PR...
>> * ...simply moved the **original code** of `StringBuilder` to become the de-facto implementation of `Reader.of()`, then stripped synchronized from it on the left hand, but kept just a synchronized wrapper on the right hand. Then added a `switch` for optimizations within the original code, at the exact location where previously just an optimization for `String` lived in.
>> * ...added tests for all methods (`Of.java`), and applied that test upon the modified `StringBuilder`.
>> 
>> Wherever new JavaDocs were added, existing phrases from other code locations have been copied and adapted, to best match the same wording.
>
> Markus KARG has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fixup! Reader.of(String)
>   
>   Dropping non-public JavaDocs

src/java.base/share/classes/java/io/Reader.java line 144:

> 142: 
> 143:     /**
> 144:      * Returns a new {@code Reader} whose source is a {@link CharSequence}.

Probably better to more this more precise, e.g.  Returns a {@code Reader} that reads characters from a {@code CharSequence}, starting at the first character in the sequence.

src/java.base/share/classes/java/io/Reader.java line 154:

> 152:      * have no effect.
> 153:      *
> 154:      * <p> After the reader has been closed, the {@code read()},

This paragraph is okay but the Reader methods shouldn't specify this (doing so after 25+ years of being unspecified would require being confident wouldn't invalidate any existing Readers).

src/java.base/share/classes/java/io/Reader.java line 159:

> 157:      * {@code transferTo()} methods all throw {@code IOException}.
> 158:      *
> 159:      * <p> The {@code markSupported()} method returns {@code true}.

Chen's suggestion to say that it supports the mark operation would be clearer than the legacy wording.

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PR Review Comment: https://git.openjdk.org/jdk/pull/21371#discussion_r1789193444
PR Review Comment: https://git.openjdk.org/jdk/pull/21371#discussion_r1789194414
PR Review Comment: https://git.openjdk.org/jdk/pull/21371#discussion_r1789195170