title: Save a list of unique Strings in the ArrayList
body: <p>I read data from a text file, so there may be:</p>
  
  <pre>
  John
  Mary
  John
  Leeds
  </pre>
  
  <p>I now need to get 3 unique elements in the ArrayList, because there are only 3 unique values in the file output (as above).</p>
  
  <p>I can use a HashTable and add information to it, then simply copy its data into the List.
  Are there other solutions? </p>