RFR: 8361018: Eliminate unnecessary buffering and encoding conversion in BufferedWriter

[Lei Zhu]

On Fri, 27 Jun 2025 16:48:40 GMT, Shaojin Wen <swen at openjdk.org> wrote:

> BufferedWriter -> OutputStreamWriter -> StreamEncoder
> 
> In this call chain, BufferedWriter has a char[] buffer, and StreamEncoder has a ByteBuffer. There are two layers of cache here, or the BufferedWriter layer can be removed. And when charset is UTF8, if the content of write(String) is LATIN1, a conversion from LATIN1 to UTF16 and then to LATIN1 will occur here.
> 
> LATIN1 -> UTF16 -> UTF8
> 
> We can improve BufferedWriter. When the parameter Writer instanceof OutputStreamWriter is passed in, remove the cache and call it directly. In addition, improve write(String) in StreamEncoder to avoid unnecessary encoding conversion.

src/java.base/share/classes/sun/nio/cs/StreamEncoder.java line 3:

> 1: /*
> 2:  * Copyright (c) 2001, 2025, Oracle and/or its affiliates. All rights reserved.
> 3:  * Copyright (c) 2054, Alibaba Group Holding Limited. All Rights Reserved.

`Copyright (c) 2054` should be `Copyright (c) 2025` ?

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PR Review Comment: https://git.openjdk.org/jdk/pull/26022#discussion_r2174234524