Construct A String Using StringBuilder from a List using elements index
As far as your code is concerned, it would be more efficient to apply the strings from the first 2 and the last elements outside the loop.  This will eliminate 3 elements from the loop:

String buildObject(List&lt;Integer&gt; obj){
   StringBuilder name = new StringBuilder();
   name.append(obj.get(0))
       .append(" &amp; ")
       .append(obj.get(1));
   int limit = obj.size() - 1;
   for(int i = 2; i &lt; limit; i++){
       name.append(", ");
           .append(obj.get(i));
   }
   name.append(" and ")
       .append(obj.get(limit));
   return name.toString();
}