Couple of measurements of object size in Java

Build:

./gradlew build

Run:

./gradlew run

Guides how to measure object size:

• https://www.baeldung.com/java-size-of-object
• https://www.javaspecialists.eu/archive/Issue142.html
• https://stackoverflow.com/questions/54162849/can-i-measure-the-size-of-a-list-in-the-memory-including-elements-using-instrume
• https://github.com/jbellis/jamm

Mutable vs immutable collections in terms of size

Comparision between:

• Standard JDK mutable collections
• Persistent collections https://github.com/hrldcpr/pcollections
• Eclipse collections mutable and immutable https://github.com/eclipse/eclipse-collections
• Guava immutable collections
• Java immutable collections https://github.com/brianburton/java-immutable-collections
• Androidx collections like ArraySet, SparseArray

List with 100 000 items

List<Integer>	Size in bytes
Integer[]	1997968
ArrayList	1997992
JImmutableTreeList	2064624
JImmutableLinkedStack	3997976
LinkedList	3997984
ConsPStack	4797984
TreePVector	5598048

Set with 100 000 items

Set<Integer>	Size in bytes
Integer[]	1997968
ArraySet	2398016
JImmutableTreeSet	5598032
TreeSet	5598032
HashSet	5846624
JImmutableHashSet	9246216
MapPSet	11198104

Map with 100 000 items

Map<Integer, Integer>	Size in bytes
Integer[]	1997968
SparseArrayCompat	2646576
ArrayMap	3186664
EclipseMutableMap	3695152
EclipseImmutableMap	3695168
TreeMap	5598000
JImmutableTreeMap	5598008
IntTreePMap	5598024
HashMap	5846608
GuavaImmutableMap	6495176
LinkedHashMap	6646600
JImmutableHashMap	9246200
HashPMap	11198088