// create Ordered set Set mySet = new LinkedHashSet (); mySet.add( str ); // union Set union = new HashSet (s1); union.addAll(s2); Set intersection = new HashSet (s1); intersection.retainAll(s2); Set difference = new HashSet (s1); difference.removeAll(s2); /// iteratate set element String[] arr = (String[]) mySet.toArray(new String[ mySet.size()]); int setSize = arr.length; for(int c=0; c < setSize;c++) { if(c==setSize-1) bufCell_Uniprot.append(arr[c]+"\n"); else bufCell_Uniprot.append(arr[c]+","); } /// iteratate set element Iterator itr = mySet.iterator(); while( itr.hasNext()) { bout.write( itr.next() +"\n"); }