RFR: String.join(), StringJoiner additions (original) (raw)

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:

http://cr.openjdk.java.net/~mduigou/JDK-8006627/2/webrev/src/share/classes/sun/misc/JavaLangAccess.java.patch

It's not merged yet though.



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