On Thu, 20 Jun 2019 at 13:53, Сергей Цыпанов <sergei.tsypa...@yandex.ru> wrote: > > On JDK 11 I've got the following results > > https://github.com/stsypanov/strings/blob/master/results/StringBuilderVsStringJoinerBenchmark.txt > > In other words StringJoiner wins when we have longer Strings or more of them > because we don't need to reallocate underlying array of StringBuilder and > check it's bounds when appending. Instead we can allocate storage only once > in StringJoine::toString.
Hi, Yes, StringJoiner is really good at joining Strings (hence the name). But it is not very good at joining primitives. Because you have to convert each primitive to a String before you can add it. StringBuilder does not need to allocate a String when you add a primitive. Try running the same test but this time with int[] instead of String[]. And I'm 100% sure that StringBuilder will be fastest. /Kasper
