How do I use Apex to create a comma separated list of strings without a trailing comma?

Question

I am having a list of String letterString

List<String> letterString = ['Jan', 'Feb', 'Mar'];

Below is teh output I want :

String outputString = 'Jan,Feb,Mar';

This is what I have done :

  String outputString = '';
  for(String s : letterString) {
      outputString += s+',';
  }

But outputString is Jan,Feb,Mar, with an extra , at an end of string.

Can't you use the traditional "for loop" to solve this ?. salesforce.com/us/developer/docs/apexcode/Content/… — ZenSeeker, Dec 21 '14 at 15:57
@UnderDog : As you can see I was trying to solve this by using the traditional for loop.I was not aware of ` string.Join()`. But if it can be done by using 1 line of code, why to go 5 lines of code. :) — SFDC Geek, Dec 21 '14 at 16:20
I meant this form of "for loop" for (init_stmt; exit_condition; increment_stmt) { code_block } and NOT for (variable : list_or_set) { code_block } — ZenSeeker, Dec 21 '14 at 16:24

Alex Tennant · Accepted Answer · 2014-12-21 12:36:28Z

This is as expected. The comma is still being appended in the last iteration of the loop even though there are no further records to be appended.

You could do some changes around the index being added or remove the trailing comma after the loop to make it work.

However, you could save yourself the hassle and use the built in String.join(Object, String) method.

String outputString = String.join(letterString, ',');

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