RFR: String.join(), StringJoiner additions

[Jim Gish]

On 04/18/2013 08:49 AM, Ulf Zibis wrote:
> 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);
I started off with something similar, but it was stripped out when Henry 
did the performance improvements.
Given that most people feel that this is going to be put to heavy-weight 
usage, it doesn't seem to merit too much emphasis on performance or 
complicating the implementation at this point.

Thanks
>
> 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 <code></code>. 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::
>>>>
>>>> - <blockquote> isn't needed around <pre> as it's already a <div> you
>>>> probably mean to do
>>>>
>>>> <pre> {@code
>>>> ...
>>>> }</pre>
>>>>
>>>> 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
>>>
>>>
>

-- 
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