RFR: String.join(), StringJoiner additions

Steven Schlansker stevenschlansker at gmail.com
Mon Apr 15 20:03:12 UTC 2013

On Apr 15, 2013, at 12:21 PM, Martin Buchholz <martinrb at google.com> wrote:

> On Mon, Apr 15, 2013 at 11:31 AM, Martin Buchholz <martinrb at google.com>wrote:
>> OTOH, I'm guessing you are trying to improve the performance of operations
>> like List.toString.
>> More efficient (single copy char[]) would be to collect all the
>> sub-CharSequences in a CharSequence[],  pre-compute the final length of the
>> char[], allocate an array of exactly the required length, and create the
>> final string directly from that using the package-private constructor (but
>> in the unlikely event that a subsequence changed in size while concat'ing,
>> be prepared to resize the array).
> Proceeding further along this train of thought, I might start with
> AbstractCollection.toString() (and similar methods) and attempt to make it
> maximally efficient.
> Maybe add a method to JavaLangAccess to make a String directly from a
> perfectly sized array (as needed elsewhere?).  Maybe create a
> StringBuilder-like class that works better for typical use cases?

For what it's worth, a patch that I contributed and Mike (and others) then rewrote
contains this functionality already:


It's not merged yet though.

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