First lambda, formatter for StringJoiner?

Paul Sandoz paul.sandoz at
Mon Jun 24 01:38:59 PDT 2013

HI Brendan,

You can use a map operation to format elements to a String before collecting.

BTW the latest source code renamed toStringJoiner to joining and now hides the use of the StringJoiner class.


On Jun 21, 2013, at 9:39 PM, Brenden Towey <brendentowey at> wrote:

> Hi all,
> I played around with the Java 8 early access build for the first time 
> last week.  Overall it was fun and I learned a bit.  One thing struck me 
> looking at the Collectors.toStringJoiner() method:
> StringJoiner is pretty neat but it could use a formatter string, like 
> java.util.Formatter.  It's a common pattern to need to format objects as 
> one collects them into a string.  For example, a stream of bytes will 
> often need to be formatted as two character hexidecimal strings, rather 
> than the default decimal representation.
> Adding a formatter string both to StringJoiner's ctor as well as to the 
> static convenience method in Collectors would be a big boon to Java 
> programmers everywhere.
> OK, that's my 2 cents!  Good luck folks.
> Brenden

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