title: Convert Enum list to comma separated String with matching Enum value
body: <p>I have a List of Enum values like MON, TUE, WED, etc., same need to convert to comma-separated String. Need to use Java 8 to convert the same in an efficient way.
  For example.</p>
  
  <pre><code>Arrays.stream(Days.values())
      .map(MON -&gt; TimeRangeConstants.MON)
      .collect(Collectors.joining(","));
  </code></pre>
  
  <pre><code>enum Days {
     MON, TUE, WED, THU, FRI, SAT, SUN;
  }
  
  main() {
     Days v1 = Days.MON;
     Days v2 = Days.WED;
     Days v3 = Days.FRI;
     List&lt;Days&gt; days = new ArrayList&lt;&gt;();
     days.add(v1);
     days.add(v2);
     days.add(v3);
      String str = convertToString(days);
  }
  
  
  convertToString(List&lt;Days&gt; list) {      
     // need to return String as "Monday, Wednesday, Friday" 
  }
  </code></pre>
  
  <p>For the given above example, I need output as "Monday, Wednesday, Friday"</p>