Why can you not insert Objects in List in natural order?

Question

This is a more theoretically question:
I need a dynamic structure to sample informations in a natural order ( by implementing the Comparable-Interface). Set and Map offers natural order but I can't use them (Set-elements are unique and I don't want to implement a <key><value> relationsship for Map).
Are there others solutions than to add the elements in a List in natural order hand made?
Thanks !

Answer 1

Here's a Collection implementation that ensures all elements are allways ordered.
It can be improved for speed, and maybe functionality, but the important thing is that it doesn't break the Collection interface and it's simple.
Have a look and maybe base your implementation on this one.
import java.util.*;
public class SortedCollection
    extends AbstractCollection
    implements Collection {
    private List elements;
    private Comparator comparator;
    public SortedCollection() {
        this.elements = new ArrayList();
    public SortedCollection(Comparator comparator) {
        this();
        this.comparator = comparator;
    public Iterator iterator() {
        return this.elements.iterator();
    public int size() {
        return this.elements.size();
    private void resort() {
        if (this.comparator == null) {
            Collections.sort(this.elements);
        } else {
            Collections.sort(this.elements, this.comparator);
    public boolean add(Object object) {
        boolean answer = this.elements.add(object);
        this.resort();
        return answer;
    public boolean addAll(Collection collection) {
        boolean answer = this.elements.addAll(collection);
        this.resort();
        return answer;
}