A quick and easy way to join array elements with a

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• Java: function for arrays like PHP's join()? 22 answers

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I'm looking for a quick and easy way to do exactly the opposite of split so that it will cause ["a","b","c"] to become "a,b,c"

Iterating through an array requires either adding a condition (if this is not the last element, add the seperator) or using substring to remove the last separator.

I'm sure there is a certified, efficient way to do it (Apache Commons?)

How do you prefer doing it in your projects?

Answer 1

it's in StringUtils:

http://www.java2s.com/Code/JavaAPI/org.apache.commons.lang/StringUtilsjoinObjectarrayStringseparator.htm

Answer 2

I prefer Google Collections over Apache StringUtils for this particular problem:

Joiner.on(separator).join(array)

Compared to StringUtils, the Joiner API has a fluent design and is a bit more flexible, e.g. null elements may be skipped or replaced by a placeholder. Also, Joiner has a feature for joining maps with a separator between key and value.

Answer 3

With Java 1.8 there is a new StringJoiner class - so no need for Guava or Apache Commons:

String str = new StringJoiner(",").add("a").add("b").add("c").toString();

Or using a collection directly with the new stream api:

String str = Arrays.asList("a", "b", "c").stream().collect(Collectors.joining(","));