yeah perhaps this is enough. Though users of appendReplacement are presumably after high performance loops or they'd be using a higher level API like replaceAll. I just can't imagine people using this API hit the format code exception in normal usage, and it's not like java is dumping junk into the StringBuilder when it throws the exception -- it pushed the correct replacement up to the error.
Maybe I can catch exceptions, roll back the builder using setLength, and rethrow. Isaac On Tue, Apr 24, 2018 at 9:38 PM, Xueming Shen <xueming.s...@oracle.com> wrote: > for String based replaceAll/First() it might be worth doing something like > > http://cr.openjdk.java.net/~sherman/regex_removesb/webrev/ > > > On 4/24/18, 10:47 AM, Isaac Levy wrote: >> >> Hi Sherman, >> >> Thanks for clarifying. Looks like exceptions are caused by invalid >> format string. I wouldn't expect most programs to be catching this and >> preserving their buffer, but dunno. >> >> How much does it affect perf? Well it depends on use case, a jmh of >> replaceAll with a length 200 string of digits and regex "(\w)" shows >> about 30% speedup. >> >> [info] Benchmark Mode Cnt Score Error Units >> [info] origM avgt 10 11.669 ± 0.211 us/op >> [info] newM avgt 10 8.926 ± 0.095 us/op >> >> Isaac >> >> >> On Tue, Apr 24, 2018 at 12:53 PM, Xueming Shen<xueming.s...@oracle.com> >> wrote: >>> >>> Hi Isaac, >>> >>> I actually meant to say "we are not supposed to output the partial text >>> into >>> the output buffer in case of an exception". It has nothing to do with the >>> changeset you cited. This has been the behavior since day one/JDK1.4, >>> though it is not specified explicitly in the API doc. The newly added >>> StringBuilder variant simply follows this behavior. If it's really >>> desired >>> it >>> is kinda doable to save that StringBuilder without the "incompatible" >>> behavior >>> change but just wonder if it is really worth the effort. >>> >>> Thanks, >>> Sherman >>> >>> >>> On 4/24/18, 9:11 AM, Isaac Levy wrote: >>>> >>>> (moving this to a separate discussion) >>>> >>>> >>>> --- a/src/java.base/share/classes/java/util/regex/Matcher.java >>>> +++ b/src/java.base/share/classes/java/util/regex/Matcher.java >>>> @@ -993,13 +993,11 @@ >>>> public Matcher appendReplacement(StringBuilder sb, String >>>> replacement) { >>>> // If no match, return error >>>> if (first< 0) >>>> throw new IllegalStateException("No match available"); >>>> - StringBuilder result = new StringBuilder(); >>>> - appendExpandedReplacement(replacement, result); >>>> // Append the intervening text >>>> sb.append(text, lastAppendPosition, first); >>>> // Append the match substitution >>>> + appendExpandedReplacement(replacement, sb); >>>> - sb.append(result); >>>> >>>> >>>> >>>> On Mon, Apr 23, 2018 at 5:05 PM Xueming Shen<xueming.s...@oracle.com> >>>> wrote: >>>>> >>>>> >>>>> I would assume in case of an exception thrown from >>>>> appendExpandedReplacement() we don't >>>>> want "text" to be pushed into the "sb". >>>>> >>>>> -sherman >>>> >>>> >>>> Perhaps. Though the behavior under exception is undefined and this >>>> function is probably primarily used though the replaceAll API, which >>>> wouldn’t return the intermediate sb under the case of exception. >>>> >>>> My reading of the blame was the temp StringBuilder was an artifact of >>>> the api previously using StringBuffer externally. See >>>> http://hg.openjdk.java.net/jdk9/dev/jdk/rev/763c564451b3 >>> >>> >
