On Fri, 28 Jun 2024 16:29:02 GMT, Paul Sandoz <psan...@openjdk.org> wrote:
>> Shaojin Wen has updated the pull request incrementally with one additional
>> commit since the last revision:
>>
>> fix comment
>
> That's a clever change and more preferable (but still potentially fragile in
> the source to bytecode translation process). However I still don't understand
> the overall motivation, why does it matter?
@PaulSandoz
String.format is widely used. In some performance-critical scenarios, when
doing performance profiling, it is often found that String.format calls consume
a lot of time. My suggestion is to replace `String.format` with `String concat`
or StringBuilder.
String info = String.format("xxxx %s", str);
replace to
String info = "xxxx %s" + str;
or
String info = new StringBuilder("xxxx ").append(str).toString();
Let's do a Benchmark comparison:
class StringFormat{
@Benchmark
public String stringIntFormat() {
return "%s %d".formatted(s, i);
}
@Benchmark
public String stringIntIndy() {
return s + " " + i;
}
@Benchmark
public String stringIntStringBuilder() {
return new StringBuilder(s).append(" ").append(i).toString();
}
}
Benchmark Mode Cnt Score Error Units
StringFormat.stringIntFormat avgt 15 87.451 ? 2.890 ns/op
StringFormat.stringIntIndy avgt 15 6.471 ? 0.089 ns/op
StringFormat.stringIntStringBuilder avgt 15 7.949 ? 0.067 ns/op
It can be seen that the performance of using StringConcat and StringBuilder is
10 times that of using String.format.
StringTemplate (JEP 430/459/465) was an attempt to improve performance, but the
API was not friendly.
I was going to contribute to StringTemplate, (PR #16044 / PR #16021/PR #16017,)
but StringTemplate has been removed.
I'm working on improving the performance of String.format.
The PR I submitted before: [8316704: Regex-free parsing of Formatter and
FormatProcessor specifiers](https://github.com/openjdk/jdk/pull/15776)
This PR is a very minor improvement, We may also need to do further work to
provide a fastpath for common scenarios to improve performance. I also plan to
do such work.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/19926#issuecomment-2197391335
