RFR: String.join(), StringJoiner additions

Mike Duigou mike.duigou at oracle.com
Mon Apr 15 22:41:23 UTC 2013

On Apr 15 2013, at 13:03 , Steven Schlansker wrote:

> 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:
> http://cr.openjdk.java.net/~mduigou/JDK-8006627/2/webrev/src/share/classes/sun/misc/JavaLangAccess.java.patch
> It's not merged yet though.

It is not forgotten. :-)


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