Patricia Shanahan <pats@acm.org> writes:
That approach was one of my first suggestions,
Sorry, I must have missed that.
but the OP wants to be able to insert items at arbitrary
positions, not according to Comparable order, or even a
Comparator.
Actually, it could be done.
For example, the ordered set might have been: |1, 2|
Now, to insert ?4? into the middle, i.e., to get |1, 4, 2|,
- add ?4? to the set
- make sure that the ordering relation will evaluate as follows
(1,4)=1
(1,2)=1
(4,2)=1
(x,y)=-(y,x)
(x,x)=0
This includes, possibly changing the Comparator at run-time.
It might not be a good for anything, so it might be idle
to write about this, but it is not impossible either.
I did think of an evil variant using a TreeMap<BigDecimal,Whatever>. An
insert into an empty structure uses key 0. An insert at the start of a
non-empty uses key one less than the current lowest key. Similarly,
insert at the end by using key one greater than the current highest key.