Remove duplicates from ArrayLists

Question

I have an ArrayList of custom objects. I want to remove duplicate entries.

The objects have three fields: title, subtitle, and id. If a su

Answer 1

You can use an O(n^2) solution: Use list.iterator() to iterate the list once, and on each iteration, iterate it again to check if there are duplicates. If there are - call iterator.remove(). A variation of this is to use guava's Iterables.filter(list, predicate) where your filtering logic is in the predicate.

Another way (perhaps better) would be to define the equals(..) and hashCode(..) methods to handle your custom equality logic, and then simply construct a new HashSet(list). This will clear duplicates.