Question

My question, is, whether the sequence of elements picked from a list will always be the same,

is this construction behaviour is deterministic for

           java "List"s - descendants of java.util.List

2) question, if I use

for(Object o: list)

construction and inside the loop’s body increment a variable,
will it be the index of list’s elements? So, how it goes through list’s elements, from 0 to size()-1 or chaotically?

                   List.get(i) 

will always return this element?

3) question ( I suppose for the 2-nd question the answer will be negative, so:)

         for (int i=0; i < list.size(); i++) {
         }

is the best way if I need to save the index of an element and later get it back from a list by its id?

Overall:

I simply need to save a position in the list in every object’s field.

        object.setPosInList(currentIndexOfTheLoop)

Now clear?

Answer 1

1) Yes

2) Yes

3) No.

Also note that on LinkedLists using get(i) is O(i) while getting the next element from an iterator (which is what for-each does) is O(1).