Remove duplicates from List using Guava

Question

How can we remove duplicates from List with the help of Guava api?

Currently I am following this:

private List removeDuplic         


        

Answer 1

I really don't recommend using (Linked)HashMultiSet to do task which is usually done with ArrayList and (Linked)HashSet like OP mentioned above - it's less readable for regular Java programmer and (probably) less efficient.

Instead, at least use static factory constructors like newArrayList and newLinkedHashSet to avoid all these s:

private static  List removeDuplicate(final List list) {
  return Lists.newArrayList(Sets.newLinkedHashSet(list));
}

However, you can do it in more "Guava way" - by avoiding nulls and using immutable collections.

So if your collection cannot have null elements, I'd suggest using immutable set instead of mutable and less efficient one:

private static  List removeDuplicate(final List list) {
  return Lists.newArrayList(ImmutableSet.copyOf(list));
}

It's still copying objects twice, so consider being fully-immutable and changing method signature to return ImmutableList:

private static  ImmutableList removeDuplicate(final List list) {
  return ImmutableSet.copyOf(list).asList();
}

This way there is only one copying involved, because ImmutableCollection.asList() returns a view.