Question

This is profoundly simple, yet I’ve seen many variants, and I don’t see my own practice much elsewhere. Given:

Iterable<String> strings;

create a String containing all the strings, separated by commas.

Answer 1

Java-8 version

With Java 8, luckily, there is finally a standard way to do this:

String string = StreamSupport.stream(strings.spliterator(), false)
                             .collect(Collectors.joining(", "));

Unfortunately, there’s not an easier way to get from an Iterable to a Stream (yet)

Pre Java-8 version

Use

org.apache.commons.lang.StringUtils.join(Iterator iterator, String separator)

From

http://commons.apache.org/lang/

If you want to do it yourself, I sometimes do

StringBuilder sb = new StringBuilder();
String separator = "";
for (String string : iterable) {
  sb.append(separator);
  sb.append(string);
  separator = ", ";
}