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

Ulf Zibis Ulf.Zibis at CoSoCo.de
Thu Apr 18 12:49:32 UTC 2013

Hi,

I'm wondering, that StringJoiner has some logic for pre/suffix, but nothing to loop the elements themselves :-(

To me, StringJoiner is a useless complicated box around StringBuilder, and imagine, someone needs thread-safety. It also slows down performance, as it needs additional instances and additional class to be loaded (critical at VM startup).

Instead please add to StringBuilder and StringBuffer: append(CharSequence... elements); append(char delimiter, CharSequence... elements); append(char delimiter, Iterable<? extends CharSequence> elements); cut(int len); // removes len chars at the end of the sequence optional: append(CharSequence delimiter, CharSequence... elements); append(CharSequence delimiter, Iterable<? extends CharSequence> elements);

For performance reasons, append should always append the trailing delimeter, which could be cut at the end.

It's questionable, if class string needs a static (=no relation to an existing string in contrast to non-static split()) join method, as it seduces to "[" + String.join(...) + "]" which needs some effort from javac side to optimize to a single StringBuilder task. IMO we better had StringBuilder.join(...), so javac could easily optimize to: new StringBuilder().append('[').append(',', someStrings).cut(1).append(']').toString()

-Ulf

Am 18.04.2013 00:07, schrieb Martin Buchholz:

I'm still wondering about whether a joiner utility should support a prefix and suffix. The obvious uses for this are collection class toString methods, but we already know that we can and should implement those with a single precise char[] construction, so should not use StringJoiner, or at least not this StringJoiner implementation. And if we're just talking about pure convenience, it's hard to beat

"[" + String.join(...) + "]"

On Wed, Apr 17, 2013 at 2:49 PM, Jim Gish <jim.gish at oracle.com> wrote: Here's an update: http://cr.openjdk.java.net/~** jgish/Bugs-5015163-7172553/<http://cr.openjdk.java.net/~jgish/Bugs-5015163-7172553/><_ _http://cr.openjdk.java.net/%**7Ejgish/Bugs-5015163-7172553/<http://cr.openjdk.java.net/%7Ejgish/Bugs-5015163-7172553/> Jim

On 04/17/2013 03:15 PM, Mike Duigou wrote: String:: line 1253: This should use {@code } rather than . I think regular spaces are OK as well.   seems inappropriate. lines 2425/2467: elements may not be null either. I can tell you (or maybe it's just me) are itching to change : for (CharSequence cs: elements) { 2477 joiner.add(cs); 2478 } to: elements.forEach(joiner::add); StringJoiner:: -

isn't needed around 
 as it's already a 
 you
probably mean to do 
 {@code
 ... } for code samples. - It would be nice if the empty output generation in three arg constructor could be suppressed unless needed. Perhaps a special (not null please!) sentinel value? - Four arg constructor doesn't include emptyOutput in @throws NPE

On Apr 11 2013, at 15:33 , Jim Gish 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

-- 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

More information about the core-libs-dev mailing list