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?
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;
}
}