LinkedHashSet - insertion order and duplicates - keep newest "on top"

Question

I need a collection that keeps insertion order and has unique values. LinkedHashSet looks like the way to go, but there's one problem - when two items are equal, it removes the newest one (which makes sense), here's an example:

set.add("one"); set.add("two"); set.add("three"); set.add("two"); 

The LinkedHashSet will print:

one, two, three

But what I need is:

one, three, two

What would be the best solution here? Is there any collection/collections method that can do this or should I implement it manually?

Answer 1

Most of the Java Collections can be extended for tweaking.

Subclass LinkedHashSet, overriding the add method.

class TweakedHashSet<T> extends LinkedHashSet<T> {      @Override     public boolean add(T e) {         // Get rid of old one.         boolean wasThere = remove(e);         // Add it.         super.add(e);         // Contract is "true if this set did not already contain the specified element"         return !wasThere;     }  }