I used Java Object Layout (JOL) to look at memory footprint for Bitset vs Boolean Objects.
I compared Bitset vs Boolean solutions for comparing classes with:
- 3 fields
- 33 fields
BITSET 3 fields class: com.example.demo.ShowBitset object internals:
| OFF | SZ | TYPE DESCRIPTION | VALUE |
|---|---|---|---|
| 0 | 8 | (object header: mark) | 0x0000000000000001 (non-biasable; age: 0) |
| 8 | 4 | (object header: class) | 0x010d7658 |
| 12 | 4 | java.lang.String ShowBitset.id | (object) |
| 16 | 4 | java.lang.String ShowBitset.title | (object) |
| 20 | 4 | java.lang.Integer ShowBitset.releaseYear | 2010 |
| 24 | 4 | java.util.BitSet ShowBitset.fieldsPresent | (object) |
| 28 | 4 | (object alignment gap) | |
| Instance size: 32 bytes | |||
| Space losses: 0 bytes internal + 4 bytes external = 4 bytes total |
BOOLEAN 3 fields class: com.example.demo.ShowBoolean object internals:
| OFF | SZ | TYPE DESCRIPTION | VALUE |
|---|---|---|---|
| 0 | 8 | (object header: mark) | 0x0000000000000001 (non-biasable; age: 0) |
| 8 | 4 | (object header: class) | 0x010d7898 |
| 12 | 1 | boolean ShowBoolean.isIdDefined | true |
| 13 | 1 | boolean ShowBoolean.isTitleDefined | true |
| 14 | 1 | boolean ShowBoolean.isReleaseYearDefined | true |
| 15 | 1 | (alignment/padding gap) | |
| 16 | 4 | java.lang.String ShowBoolean.id | (object) |
| 20 | 4 | java.lang.String ShowBoolean.title | (object) |
| 24 | 4 | java.lang.Integer ShowBoolean.releaseYear | 2010 |
| 28 | 4 | (object alignment gap) | |
| Instance size: 32 bytes | |||
| Space losses: 1 bytes internal + 4 bytes external = 5 bytes total |
Both Bitset and Boolean based solutions fare similarly for both solutions.
BITSET 33 fields class: com.example.demo.UpdateShowInputBitset object internals:
| OFF | SZ | TYPE DESCRIPTION | VALUE |
|---|---|---|---|
| 0 | 8 | (object header: mark) | 0x0000000000000001 (non-biasable; age: 0) |
| 8 | 4 | (object header: class) | 0x010d7af0 |
| 12 | 4 | java.lang.String UpdateShowInputBitset.id | (object) |
| 16 | 4 | java.lang.String UpdateShowInputBitset.title | (object) |
| 20 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear | 2024 |
| 24 | 4 | java.lang.String UpdateShowInputBitset.id1 | (object) |
| 28 | 4 | java.lang.String UpdateShowInputBitset.title1 | (object) |
| 32 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear1 | 2024 |
| 36 | 4 | java.lang.String UpdateShowInputBitset.id2 | (object) |
| 40 | 4 | java.lang.String UpdateShowInputBitset.title2 | (object) |
| 44 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear2 | 2024 |
| 48 | 4 | java.lang.String UpdateShowInputBitset.id3 | (object) |
| 52 | 4 | java.lang.String UpdateShowInputBitset.title3 | (object) |
| 56 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear3 | 2024 |
| 60 | 4 | java.lang.String UpdateShowInputBitset.id4 | (object) |
| 64 | 4 | java.lang.String UpdateShowInputBitset.title4 | (object) |
| 68 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear4 | 2024 |
| 72 | 4 | java.lang.String UpdateShowInputBitset.id5 | (object) |
| 76 | 4 | java.lang.String UpdateShowInputBitset.title5 | (object) |
| 80 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear5 | 2024 |
| 84 | 4 | java.lang.String UpdateShowInputBitset.id6 | (object) |
| 88 | 4 | java.lang.String UpdateShowInputBitset.title6 | (object) |
| 92 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear6 | 2024 |
| 96 | 4 | java.lang.String UpdateShowInputBitset.id7 | (object) |
| 100 | 4 | java.lang.String UpdateShowInputBitset.title7 | (object) |
| 104 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear7 | 2024 |
| 108 | 4 | java.lang.String UpdateShowInputBitset.id8 | (object) |
| 112 | 4 | java.lang.String UpdateShowInputBitset.title8 | (object) |
| 116 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear8 | 2024 |
| 120 | 4 | java.lang.String UpdateShowInputBitset.id9 | (object) |
| 124 | 4 | java.lang.String UpdateShowInputBitset.title9 | (object) |
| 128 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear9 | 2024 |
| 132 | 4 | java.lang.String UpdateShowInputBitset.id10 | (object) |
| 136 | 4 | java.lang.String UpdateShowInputBitset.title10 | (object) |
| 140 | 4 | java.lang.Integer UpdateShowInputBitset.releaseYear10 | 2024 |
| 144 | 4 | java.util.BitSet UpdateShowInputBitset.fieldsPresent | (object) |
| 148 | 4 (object alignment gap) | ||
| Instance size: 152 bytes | |||
| Space losses: 0 bytes internal + 4 bytes external = 4 bytes total |
BOOLEAN 33 fields class: com.example.demo.UpdateShowInputBoolean object internals:
| OFF | SZ | TYPE DESCRIPTION | VALUE |
|---|---|---|---|
| 0 | 8 | (object header: mark) | 0x0000000000000001 (non-biasable; age: 0) |
| 8 | 4 | (object header: class) | 0x010d81f8 |
| 12 | 1 | boolean UpdateShowInputBoolean.isReleaseYear10Defined | true |
| 13 | 1 | boolean UpdateShowInputBoolean.isTitleDefined | true |
| 14 | 1 | boolean UpdateShowInputBoolean.isReleaseYearDefined | true |
| 15 | 1 | boolean UpdateShowInputBoolean.isId1Defined | true |
| 16 | 1 | boolean UpdateShowInputBoolean.isTitle1Defined | true |
| 17 | 1 | boolean UpdateShowInputBoolean.isReleaseYear1Defined | true |
| 18 | 1 | boolean UpdateShowInputBoolean.isId2Defined | true |
| 19 | 1 | boolean UpdateShowInputBoolean.isTitle2Defined | true |
| 20 | 1 | boolean UpdateShowInputBoolean.isReleaseYear2Defined | true |
| 21 | 1 | boolean UpdateShowInputBoolean.isId3Defined | true |
| 22 | 1 | boolean UpdateShowInputBoolean.isTitle3Defined | true |
| 23 | 1 | boolean UpdateShowInputBoolean.isReleaseYear3Defined | true |
| 24 | 1 | boolean UpdateShowInputBoolean.isId4Defined | true |
| 25 | 1 | boolean UpdateShowInputBoolean.isTitle4Defined | true |
| 26 | 1 | boolean UpdateShowInputBoolean.isReleaseYear4Defined | true |
| 27 | 1 | boolean UpdateShowInputBoolean.isId5Defined | true |
| 28 | 1 | boolean UpdateShowInputBoolean.isTitle5Defined | true |
| 29 | 1 | boolean UpdateShowInputBoolean.isReleaseYear5Defined | true |
| 30 | 1 | boolean UpdateShowInputBoolean.isId6Defined | true |
| 31 | 1 | boolean UpdateShowInputBoolean.isTitle6Defined | true |
| 32 | 1 | boolean UpdateShowInputBoolean.isReleaseYear6Defined | true |
| 33 | 1 | boolean UpdateShowInputBoolean.isId7Defined | true |
| 34 | 1 | boolean UpdateShowInputBoolean.isTitle7Defined | true |
| 35 | 1 | boolean UpdateShowInputBoolean.isReleaseYear7Defined | true |
| 36 | 1 | boolean UpdateShowInputBoolean.isId8Defined | true |
| 37 | 1 | boolean UpdateShowInputBoolean.isTitle8Defined | true |
| 38 | 1 | boolean UpdateShowInputBoolean.isReleaseYear8Defined | true |
| 39 | 1 | boolean UpdateShowInputBoolean.isId9Defined | true |
| 40 | 1 | boolean UpdateShowInputBoolean.isTitle9Defined | true |
| 41 | 1 | boolean UpdateShowInputBoolean.isReleaseYear9Defined | true |
| 42 | 1 | boolean UpdateShowInputBoolean.isId10Defined | true |
| 43 | 1 | boolean UpdateShowInputBoolean.isTitle10Defined | true |
| 44 | 1 | boolean UpdateShowInputBoolean.isIdDefined | true |
| 45 | 3 | (alignment/padding gap) | |
| 48 | 4 | java.lang.String UpdateShowInputBoolean.id | (object) |
| 52 | 4 | java.lang.String UpdateShowInputBoolean.title | (object) |
| 56 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear | 2025 |
| 60 | 4 | java.lang.String UpdateShowInputBoolean.id1 | (object) |
| 64 | 4 | java.lang.String UpdateShowInputBoolean.title1 | (object) |
| 68 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear1 | 2025 |
| 72 | 4 | java.lang.String UpdateShowInputBoolean.id2 | (object) |
| 76 | 4 | java.lang.String UpdateShowInputBoolean.title2 | (object) |
| 80 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear2 | 2025 |
| 84 | 4 | java.lang.String UpdateShowInputBoolean.id3 | (object) |
| 88 | 4 | java.lang.String UpdateShowInputBoolean.title3 | (object) |
| 92 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear3 | 2025 |
| 96 | 4 | java.lang.String UpdateShowInputBoolean.id4 | (object) |
| 100 | 4 | java.lang.String UpdateShowInputBoolean.title4 | (object) |
| 104 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear4 | 2025 |
| 108 | 4 | java.lang.String UpdateShowInputBoolean.id5 | (object) |
| 112 | 4 | java.lang.String UpdateShowInputBoolean.title5 | (object) |
| 116 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear5 | 2025 |
| 120 | 4 | java.lang.String UpdateShowInputBoolean.id6 | (object) |
| 124 | 4 | java.lang.String UpdateShowInputBoolean.title6 | (object) |
| 128 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear6 | 2025 |
| 132 | 4 | java.lang.String UpdateShowInputBoolean.id7 | (object) |
| 136 | 4 | java.lang.String UpdateShowInputBoolean.title7 | (object) |
| 140 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear7 | 2025 |
| 144 | 4 | java.lang.String UpdateShowInputBoolean.id8 | (object) |
| 148 | 4 | java.lang.String UpdateShowInputBoolean.title8 | (object) |
| 152 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear8 | 2025 |
| 156 | 4 | java.lang.String UpdateShowInputBoolean.id9 | (object) |
| 160 | 4 | java.lang.String UpdateShowInputBoolean.title9 | (object) |
| 164 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear9 | 2025 |
| 168 | 4 | java.lang.String UpdateShowInputBoolean.id10 | (object) |
| 172 | 4 | java.lang.String UpdateShowInputBoolean.title10 | (object) |
| 176 | 4 | java.lang.Integer UpdateShowInputBoolean.releaseYear10 | 2025 |
| 180 | 4 | (object alignment gap) | |
| Instance size: 184 bytes | |||
| Space losses: 3 bytes internal + 4 bytes external = 7 bytes total |
This indicates Boolean fields consume a 1-byte space while Bitset is much more optimized for storing Boolean field values. This disparity will increase further with increase in fields.