Collections with limited size

Question

Is there any collection which allows me limit the number of elements allowed?

What I need is a collection with size of 5 elements, when this collection is full, a new element can be added, but the oldest element of this collection will be replaced for the new element.

What do you mean? So for example you want to have a list that can only have at most 5 elements, and any attempt to add more will throw an exception? — MxLDevs, May 29 '14 at 19:57
Please specify a use case. The most simple solution is the Good Old Java Array :) — Honza Zidek, May 29 '14 at 19:58
Do you mean a data structure that gives an error if you try to overfill it, or one that throws away one of the existing values to fit a newly added one? — Joachim Isaksson, May 29 '14 at 19:58
I need to do a collection with size of 5 elements, when this collection is full, a new element can be added, but the oldest element of this collection will be replaced for the new element. — hmrojas.p, May 29 '14 at 20:05

score 1 · Answer 1 · answered May 29 '14 at 20:01

You can do this with majority of the Collections available in java.utils package. You can do this,sample for List Collection:

List<X> list = Arrays.asList(new X[desiredSize]);
// where X is any Object type (including arrays and enums,
// but excluding primitives)

The resulting list is modifiable, but not resizable (i.e. add(e) and remove(e) don't work, but set(index, e) does).

score 1 · Accepted Answer · edited May 29 '14 at 20:08

1

You can extend an old good ArrayList (or any other implementation which fits you the best).

import java.util.ArrayList;

public class LimitedCollection<E> extends ArrayList<E> {

    public static final int MAX_ELEMENTS = 2;

    @Override
    public boolean add(E e) {
        if (this.size() < MAX_ELEMENTS) {
            return super.add(e);
        } else {
            return false;
        }
    }
    }

edited May 29 '14 at 20:08

Damian Leszczyński - Vash

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answered May 29 '14 at 20:07

Mirek Surma

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thanks, your solution seem great, I will work with it. – hmrojas.p May 29 '14 at 20:19
Your class should be named LimitedArrayList as you extend an array list and whats more you should also override the addAll and constructors. – Damian Leszczyński - Vash May 29 '14 at 20:20
That doesn't remove the oldest element upon addition a new one when the List reached the limit. – j3ny4 May 29 '14 at 20:24

score 0 · Answer 3 · answered May 29 '14 at 20:46

0

Either Guava EvictingQueue or Apache common-collections should do the job for you.

answered May 29 '14 at 20:46

j3ny4

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Collections with limited size

3 Answers3