Is there a ready to use Java lifo class (stack) with push to front on reinsertion?

Question

I'm looking for a Java LIFO structure with unique values. Furthermore it should promote an already inserted value to the front on reinsertion. It would be useful to track the order of focused windows for example.

I know that it isn't really hard to implement by extending or using Stack or LinkedHashSet, but maybe I missed an already existing implementation in the standard Java classes.

An ordered set might be better than a stack for this, as it has unique values and is still sorted. Not sure how hard would it be to move a again-inserted element on start (probably not much). — kajacx, Jul 08 '14 at 11:29

Jamie Cockburn · Accepted Answer · 2014-07-08T11:54:05.717

2

Not that I'm aware of, but this would do the trick:

class ReinsertionStack<E> extends Stack<E> {
    @Override
    public E push(E item) {
        this.remove(item);
        return super.push(item);
    }
}

This also guarantees uniqueness so long as you only add to the stack via push().

edited Jul 08 '14 at 11:54

answered Jul 08 '14 at 11:32

Jamie Cockburn

7,379
1
24
37

Can't this be simplified to just `remove(item); super.push(item);`? – Ordous Jul 08 '14 at 11:37
No, the OP wanted push at front on reinsertion. That would be at the back. – Jamie Cockburn Jul 08 '14 at 11:39
3

I think we have very different ideas of what a front of a stack is :) – Ordous Jul 08 '14 at 11:40
with stack why not use 'top' instead – Shailesh Aswal Jul 08 '14 at 11:41
Sorry for the confusion. I thought of top. So Ordous would be right. An I implemented it like that myself, also overriding add,addAll,addElement, but I hoped that I missed a standard class doing that. – raffael Jul 08 '14 at 11:52

score 0 · Answer 2 · answered Jul 08 '14 at 11:32

I think what you want is the Stack class http://docs.oracle.com/javase/1.5.0/docs/api/java/util/Stack.html

The methods that might interest you :

pop() Removes the object at the top of this stack and returns that object as the value of this function.

E push(E item) Pushes an item onto the top of this stack.

Hope that help.

The search method, can give you an easy way to deal with already inserted object

Is there a ready to use Java lifo class (stack) with push to front on reinsertion?

2 Answers2