Size of various JVM data structures in bytes (top column is number of elements).

sizes.txt

COLLECTION                              0        1        5       10       50      100      500     1000
Array[Int]                             16       24       40       56      216      416     2016     4016
immutable.BitSet                       24       24       24       24       24       32       96      160
immutable.IntMap[Int]                  16       40      328      688     3568     7168    35968    71968
immutable.List[Int]                    16       56      216      416     2016     4016    20016    40016
immutable.Map[Int,Int]                 16       40      304      720     4856     9680    53504   111760
immutable.Queue[Int]                   40       80      240      440     2040     4040    20040    40040
immutable.Set[Int]                     16       32      264      480     3016     5840    27696    57952
immutable.SortedMap[Int,Int]           40       88      280      520     2440     4840    30008    62008
immutable.SortedSet[Int]               40      104      296      536     2456     4856    24056    48056
immutable.Stream[Int]                  16      120      120      120      120      120      120      120
immutable.Stream[Int] (memoized)       16       56      216      416     2016     4016    20016    40016
immutable.TreeMap[Int,Int]             40       88      280      520     2440     4840    30008    62008
immutable.TreeSet[Int]                 40      104      296      536     2456     4856    24056    48056
immutable.Vector[Int]                  56      216      280      360     1288     2376    10504    20808
j.u.ArrayDeque[Int]                   104      120      184      264     1096     2152    10088    20136
j.u.ArrayList[Int]                     40       96      160      240     1136     2080    10240    20976
j.u.HashMap[Int]                       48      176      368      608     2976     5888    34128    70224
j.u.HashSet[Int]                       64      208      400      640     3008     5920    28192    56288
j.u.LinkedHashMap[Int]                 56      192      416      696     3384     6696    38136    78232
j.u.LinkedHashSet[Int]                 72      224      448      728     3416     6728    32200    64296
j.u.LinkedList[Int]                    32       72      232      432     2032     4032    20032    40032
j.u.PriorityQueue[Int]                 96      112      176      256     1048     2056    10104    20672
j.u.TreeMap[Int,Int]                   48      104      328      608     2848     5648    34016    70016
j.u.TreeSet[Int]                       64      136      360      640     2880     5680    28080    56080
j.u.Vector[Int]                        88      104      168      248     1168     2288    10608    21168
mutable.ArrayBuffer[Int]              104      120      184      264     1096     2152    10088    20136
mutable.BitSet                         40       40       40       40       40       48       96      160
mutable.Map[Int,Int]                  120      160      320      520     2568     5080    30120    62216
mutable.PriorityQueue[Int]            144      160      224      304     1136     2192    10128    20176
mutable.Set[Int]                      184      200      264      344     1368     2680    16248    32440

I updated it to differentiate a stream before evaluation (Stream[Int]) and after evaluation (Stream[Int] (memoized)).