Question

I read data from a text file, so there may be:

John
Mary
John
Leeds

I now need to get 3 unique elements in the ArrayList, because there are only 3 unique values in the file output (as above).

I can use a HashTable and add information to it, then simply copy its data into the List.
Are there other solutions?

Answer 1

Why do you need to store it in a List? Do you actually require the data to be ordered or support index-based look-ups?

I would suggest storing the data in a Set. If ordering is unimportant you should use HashSet. However, if you wish to preserve ordering you could use LinkedHashSet.