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<T> removeDuplicate(List<T> list){ return new ArrayList<T>(new LinkedHashSet<T>(list)); } 

Answer 1

Probably the most efficient way is ImmutableSet.copyOf(list).asList(), which eliminates duplicates and preserves iteration order.

(But your implementation with LinkedHashSet would be nearly as efficient, and wouldn't throw up on nulls, in the unlikely event you actually wanted nulls in your collection.)

Answer 2

I love Louis' answer for the simplicity of it (and because it's the only answer that doesn't require 2 full iterations), but unfortunately in the real world, you often encounter situations where null does occur. Here's a slightly longer null-safe version:

ImmutableSet.copyOf(     Iterables.filter(         list, Predicates.not(Predicates.isNull()))).asList(); 

Or, with static imports:

copyOf(filter(list, not(isNull()))).asList(); 

Of course you need to be aware of the fact that all null Values will be lost from the List.