Hello,

I have a list of objects say, List. The Entity class has an equals method,on few attributes ( business rule ) to differentiate one Entity object from the other.

The task that we usually carry out on this list is to remove all the duplicates something like this :

List<Entity> noDuplicates = new ArrayList<Entity>();
for(Entity entity: lstEntities)
{
    int indexOf = noDuplicates.indexOf(entity);
    if(indexOf >= 0 )
    {
            noDuplicates.get(indexOf).merge(entity);
    }
    else
    {
            noDuplicates.add(entity);
     }
}

Now, the problem that I have been observing is that this part of the code, is slowing down considerably as soon as the list has objects more than 10000.I understand arraylist is doing a o(N) search.

Is there a faster alternative, using HashMap is not an option, because the entity's uniqueness is built upon 4 of its attributes together, it would be tedious to put in the key itself into the map ? will sorted set help in faster querying ?

Thanks