Question: I'm using to show exif data of a picture.

this is the code

```
<?php

  $filename = "http://www.rallyfun.net/images/20140921231511_img_7369.jpg";

  $exif = exif_read_data($filename, 0, true);

  echo "Exposure: " . $exif["EXIF"]["ExposureTime"] . " sec.<br />";
  echo "F: " . $exif["EXIF"]["FNumber"] . "<br />";
  echo "ISO: " . $exif["EXIF"]["ISOSpeedRatings"] . "<br />";

?>

```

this is the result:

```
Exposure: 1/6400 sec.
F: 63/10 sec.
ISO: 1000

```

the result is ok except for the aperture: it must be displayed as (in this case) 6.3 so i need to divide the first number (63) with the number after the "/" (10).

how?

Answer: 
fill a set with the two lists, then convert the set back into a list (list2).

```
Set<String> set = new HashSet<String>(list2);
set.addAll(list1);
list2 = new ArrayList(set);

```
Something like

```
Set<String> stringSet = new HashSet<>(Arrays.asList(new String[]{"1","2","3"}));
stringSet.addAll(Arrays.asList(new String[]{"1","2","3","4"}));
List<String> finalList = new ArrayList<>(stringSet);

```