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

Martin Buchholz martinrb at google.com
Mon Apr 15 18:31:00 UTC 2013

It is natural to compare StringJoiner with guava Joiner. http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/base/Joiner.html Joiner is popular and has stood the test of time.

Joiner designers chose not to include a prefix and suffix, presumably because that is an independent concern - it's not a "joining" activity.

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).

On Thu, Apr 11, 2013 at 3:33 PM, Jim Gish <jim.gish at oracle.com> wrote:

Please review http://cr.openjdk.java.net/~jgish/Bugs-5015163-7175206- 7172553/ <http://cr.openjdk.java.net/~jgish/Bugs-5015163-7175206-7172553/><_ _http://cr.openjdk.java.net/%**7Ejgish/Bugs-5015163-7175206-**7172553/<http://cr.openjdk.java.net/%7Ejgish/Bugs-5015163-7175206-7172553/> >

These are changes that we made in lambda that we're now bringing into JDK8. I've made a couple of additions - making StringJoiner final and adding a couple of constructors to set the emptyOutput chars. Thanks, Jim -- Jim Gish | Consulting Member of Technical Staff | +1.781.442.0304 Oracle Java Platform Group | Core Libraries Team 35 Network Drive Burlington, MA 01803 jim.gish at oracle.com

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