Memory-efficient sparse array in Java

Question

(There are some questions about time-efficient sparse arrays but I am looking for memory efficiency.)

I need the equivalent of a List or

Answer 1

I would look at Android's SparseArray implementation for inspiration. You can view the source by downloading AOSP's source code here http://source.android.com/source/downloading.html

Answer 2

I will suggest you to use OpenIntObjectHashMap from Colt library. Link

Answer 3

I would try with trove collections, there is TIntObjectMap which can work for your intents.

Answer 4

Late to this question, but there is IntMap in libgdx which uses cuckoo hashing. If anything it would be interesting to compare with the others.

Answer 5

I have saved my test case as jglick/inthashmap. The results:

HashMap size: 1017504
TIntObjectMap size: 853216
IntHashMap size: 846984
OpenIntObjectHashMap size: 760472