> String.format is widely used, and improving its performance is very
> meaningful. This PR can significantly improve the performance of
> String.format. Sorry, there are many changes, which will take a lot of time.
> I hope you can review it patiently.
>
>
> Improved performance includes the following:
>
> ## 1. Write directly during the parse process to reduce object allocation.
>
> In the current Formatter implementation, some objects do not need to be
> allocated, such as:
>
>
> class Formatter {
> public Formatter format(Locale l, String format, Object ... args) {
> List<FormatString> fsa = parse(format);
> // ...
> }
>
> static List<FormatString> parse(String s) {
> ArrayList<FormatString> al = new ArrayList<>();
>
> while (i < max) {
> int n = s.indexOf('%', i);
> if (n < 0) {
> //
> al.add(new FixedString(s, i, max));
> }
> }
> }
> }
>
> In the process of parsing, the content that is not a Specifier is directly
> appended without going through FixedString. By directly printing the parsed
> FormatString object, there is no need to construct a `List<FormatString> fsa`
> to store it.
>
> ## 2. Fast path print
> Use specialized FormatString implementations for single-character and
> single-width specifiers to avoid calling the large FormatSpecifier#print
> method.
>
> ## 3. String.format directly calls j.u.Formatter
> String.format directly calls j.u.Formatter via SharedSecrets to improve
> performance
Shaojin Wen has updated the pull request with a new target base due to a merge
or a rebase. The pull request now contains eight commits:
- Merge remote-tracking branch 'upstream/master' into optim_str_format_202407
# Conflicts:
# src/java.base/share/classes/jdk/internal/util/DecimalDigits.java
- Implementing JavaUtilFormatterAccess using anonymous class
- Merge remote-tracking branch 'upstream/master' into optim_str_format_202407
- use unknownFormatConversion method construct UnknownFormatConversionException
- uppercase static final field name & code format
- add stable annotation
- replace cast to pattern matching
- speed up j.u.Formatter & String.format
-------------
Changes: https://git.openjdk.org/jdk/pull/20055/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20055&range=04
Stats: 680 lines in 6 files changed: 554 ins; 60 del; 66 mod
Patch: https://git.openjdk.org/jdk/pull/20055.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/20055/head:pull/20055
PR: https://git.openjdk.org/jdk/pull/20055
