I have seen that there is a very convenient way to reverse ArrayList
like here using Collections.reverse()
method, but I need to achieve such a reverse operation for several types of primitive objects, like at least ArrayList
and List
of my custom objects. So Collections
can't save my life for an extended usage of a single method.
So far I managed to get stg working (See code below) but I have to write it twice: once for ArrayList and once for List. I named them both the same so usage is very convenient, but some .. optimization would be even more convenient :-).
How to commonalize these 2 methods into a single (real) generic one ?
Thx
/**
* Generic Reverse Method for ARRAYLIST using Iterator
* @param ArrayList<Obj_item> notReversed
* @return ArrayList<Obj_item> reversed
*/
@SuppressWarnings("unchecked")
public static <Obj_item> ArrayList<Obj_item> GenReverseArrayByIterator(ArrayList<Obj_item> mylist) {
// ^^^^^^^^^^^^^^^^^^ how to make this generic ?
// Instanciate
ArrayList<Obj_item> tmp = new ArrayList<Obj_item>();
ArrayList<Obj_item> reversed = new ArrayList<Obj_item>();
// Copy original list
tmp = mylist;
// Generate an iterator, starting right after the last element.
@SuppressWarnings("rawtypes")
ListIterator myIterator = tmp.listIterator(tmp.size());
// Iterate in reverse direction
while (myIterator .hasPrevious()) {
reversed.add((Obj_item) myIterator.previous());
}
return reversed;
}
Collections.reverse
takes a List<?>
. ArrayList
implements List
- you can use that method on an ArrayList
or any List
implementation. What you're doing seems entirely unnecessary, unless I misunderstood the question.