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

Answer 1

When initializing you're LinkedHashSet you could override the add method.

Set set = new LinkedHashSet(){
    @Override
    public boolean add(String s) {
        if(contains(s))
            remove(s);
        return super.add(s);
    }
};

Now it gives you:

set.add("1");
set.add("2");
set.add("3");
set.add("1");
set.addAll(Collections.singleton("2"));

// [3, 1 ,2]

even the addAll method is working.