Thursday, October 25, 2018

A quick and easy way to join array elements with a separator (the opposite of split) in Java




See Related .NET question



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



Using Java 8 you can do this in a very clean way:



String.join(delimiter, elements);


This works in three ways:




1) directly specifying the elements



String joined1 = String.join(",", "a", "b", "c");


2) using arrays



String[] array = new String[] { "a", "b", "c" };
String joined2 = String.join(",", array);



3) using iterables



List list = Arrays.asList(array);
String joined3 = String.join(",", list);

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