title: How to convert a List<String> into a comma separated string without iterating List explicitly
body: <pre><code>List&lt;String&gt; ids = new ArrayList&lt;String&gt;();
  ids.add("1");
  ids.add("2");
  ids.add("3");
  ids.add("4");
  </code></pre>
  
  <p>Now i want an output from this list as 1,2,3,4 without <strong>explicitly</strong> iterating over it.</p>