On Thu, 12 Mar 2026 11:13:07 GMT, Eirik Bjørsnøs <[email protected]> wrote:
>> This PR optimizes string concatenation in `URL::toExternalForm`. This method
>> is called by `URL:toString` and executes often enough to be noticed during
>> startup / classloading profiling. It was previously optimized in JDK 10 via
>> JDK-8193034, but we can do more.
>>
>> Key observations:
>>
>> * The current method concatenates concatenated strings. We can get away with
>> less by flattening and concatenating once per call.
>> * The current method does not take advantage of the fact that most URL
>> components are optional and several are commonly not present. We can
>> specialize for those cheaper common concatenations.
>>
>> This PR reduces runtime with 60% or more, depending on present URL
>> components. (Benchmark results in first comment). I also ran the benchmark
>> with compilation excluded and found no regressions for the interpreter case.
>>
>> Working on this PR revealed that current tests miss coverage for the case
>> where a query or ref component is the empty string. Some new test cases are
>> added to `Constructor.java`. Otherwise, `URL::toString` seems well tested by
>> current tests.
>>
>> Performance refactoring, `noreg-perf`.
>
> Eirik Bjørsnøs has updated the pull request incrementally with seven
> additional commits since the last revision:
>
> - Add comment explaining why method is fast
> - Give up on vertical alignment
> - Shorten fast paths by using a ternary operator
> - Boolean locals for optionality allows tighter code
> - Fast paths can be moved to top of method
> - Add test cases for URLs with empty (blank, but non null) query and ref
> components
> - Fix regression caused by treating blank query or ref as not present
src/java.base/share/classes/java/net/URLStreamHandler.java line 496:
> 494: // Fast paths for empty components
> 495: if (emptyQuery && emptyRef) {
> 496: var path = emptyPath ? "" : u.getPath();
should we take that line out of the `if` block? We have the same one below line
504
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PR Review Comment: https://git.openjdk.org/jdk/pull/30151#discussion_r2924767964
