JarCastingUsage
Create interfaces for key domains and static final key instances
public interface MyCommonKeyDomain extends KeyDomain {
}
public interface MyKeyDomain1 extends MyCommonKeyDomain {
Key<MyKeyDomain1, Integer> KEY1 = new Key<>(MyKeyDomain1.class, () -> 0);
Key<MyKeyDomain1, Long> KEY2 = new Key<>(MyKeyDomain1.class, () -> 0L);
// ...
}
public interface MyKeyDomain2 extends MyCommonKeyDomain {
Key<MyKeyDomain1, BigDecimal> KEY3 = new Key<>(MyKeyDomain2.class, () -> BigDecimal.ZERO);
// ...
}
Create a typed map instance and put values
TypedByte8KeyMap<MyCommonKeyDomain, Number> map = new TypedByte8KeyMap<>();
map.put(KEY1, 8); // you can put only Integer instances for KEY1
map.put(KEY3, BigDecimal.ONE);
Use cases
As a replacement for sparsed data structures with a high probability of uninitialized fields
Suppose we have a data class (see SparsedStruct.java) of 128 fields. But only 10-15% of the fields are populated with non-null values.
So, instead of using this awful data structure you can use hashmap-like typed structure that let you code with static typing but with increased performance and reduced memory consumption.
Let's compare these approaches:
Benchmark Mode Cnt Score Error Units
SparsedStructBenchmark.byte16 thrpt 5 3928450.037 ± 100597.093 ops/s
SparsedStructBenchmark.byte16:·gc.alloc.rate thrpt 5 239.424 ± 5.997 MB/sec
SparsedStructBenchmark.byte16:·gc.alloc.rate.norm thrpt 5 96.001 ± 0.001 B/op
SparsedStructBenchmark.byte16:·gc.churn.G1_Eden_Space thrpt 5 103.488 ± 87.770 MB/sec
SparsedStructBenchmark.byte16:·gc.churn.G1_Eden_Space.norm thrpt 5 41.529 ± 36.146 B/op
SparsedStructBenchmark.byte16:·gc.churn.G1_Old_Gen thrpt 5 0.651 ± 0.023 MB/sec
SparsedStructBenchmark.byte16:·gc.churn.G1_Old_Gen.norm thrpt 5 0.261 ± 0.013 B/op
SparsedStructBenchmark.byte16:·gc.count thrpt 5 6.000 counts
SparsedStructBenchmark.byte16:·gc.time thrpt 5 24.000 ms
SparsedStructBenchmark.byte8 thrpt 5 5116186.063 ± 157104.708 ops/s
SparsedStructBenchmark.byte8:·gc.alloc.rate thrpt 5 363.745 ± 12.946 MB/sec
SparsedStructBenchmark.byte8:·gc.alloc.rate.norm thrpt 5 112.001 ± 0.001 B/op
SparsedStructBenchmark.byte8:·gc.churn.G1_Eden_Space thrpt 5 292.694 ± 2.673 MB/sec
SparsedStructBenchmark.byte8:·gc.churn.G1_Eden_Space.norm thrpt 5 90.131 ± 3.831 B/op
SparsedStructBenchmark.byte8:·gc.churn.G1_Old_Gen thrpt 5 0.653 ± 0.006 MB/sec
SparsedStructBenchmark.byte8:·gc.churn.G1_Old_Gen.norm thrpt 5 0.201 ± 0.006 B/op
SparsedStructBenchmark.byte8:·gc.count thrpt 5 10.000 counts
SparsedStructBenchmark.byte8:·gc.time thrpt 5 39.000 ms
SparsedStructBenchmark.linked thrpt 5 6298741.392 ± 234602.431 ops/s
SparsedStructBenchmark.linked:·gc.alloc.rate thrpt 5 1536.016 ± 45.973 MB/sec
SparsedStructBenchmark.linked:·gc.alloc.rate.norm thrpt 5 384.001 ± 0.001 B/op
SparsedStructBenchmark.linked:·gc.churn.G1_Eden_Space thrpt 5 1317.853 ± 11.009 MB/sec
SparsedStructBenchmark.linked:·gc.churn.G1_Eden_Space.norm thrpt 5 329.475 ± 9.633 B/op
SparsedStructBenchmark.linked:·gc.churn.G1_Old_Gen thrpt 5 0.652 ± 0.008 MB/sec
SparsedStructBenchmark.linked:·gc.churn.G1_Old_Gen.norm thrpt 5 0.163 ± 0.005 B/op
SparsedStructBenchmark.linked:·gc.count thrpt 5 20.000 counts
SparsedStructBenchmark.linked:·gc.time thrpt 5 103.000 ms
SparsedStructBenchmark.pojo thrpt 5 3679792.900 ± 1193894.983 ops/s
SparsedStructBenchmark.pojo:·gc.alloc.rate thrpt 5 1241.953 ± 409.663 MB/sec
SparsedStructBenchmark.pojo:·gc.alloc.rate.norm thrpt 5 528.001 ± 0.001 B/op
SparsedStructBenchmark.pojo:·gc.churn.G1_Eden_Space thrpt 5 1057.805 ± 1307.181 MB/sec
SparsedStructBenchmark.pojo:·gc.churn.G1_Eden_Space.norm thrpt 5 443.198 ± 438.197 B/op
SparsedStructBenchmark.pojo:·gc.churn.G1_Old_Gen thrpt 5 0.651 ± 0.013 MB/sec
SparsedStructBenchmark.pojo:·gc.churn.G1_Old_Gen.norm thrpt 5 0.278 ± 0.103 B/op
SparsedStructBenchmark.pojo:·gc.count thrpt 5 18.000 counts
SparsedStructBenchmark.pojo:·gc.time thrpt 5 89.000 ms
As a replacement for EnumMap with typed keys
As you know, java enums have an important limitation not allowing to use typed instances. You cannot do something like that
public enum MyEnum implements Interface<T> { // compilation error
KEY1<Integer>, // compilation error
KEY2<Long>
// ...
}
in enums (this feature can be added to Java 10: see Enhanced enums).
This project uses typed keys. Each key may belong to a key domain (an interface that extends base KeyDomain interface). Once created, the key receives an unique id within the most common KeyDomain interface. Some typed maps use these ids to sort entries to speed-up lookup and put operations. The most convenient way to create static final typed key instances is to declare them in interfaces, e.g.
public interface MyKeys {
Key<MyDomain, String> KEY1 = new Key<>(MyDomain.class, () -> "default value");
Key<MyDomain, Currency> KEY2 = new Key<>(MyDomain.class, () -> Currency.getInstance("BYN"));
}
As a type-safe and memory efficient replacement for Int2ObjectMap/IntObjectMap with domain keys
Performance characteristics
| Map | size | get, ns/op | put, ns/op | put GC alloc.rate, B/op | put GC time, ms |
|---|---|---|---|---|---|
| TypedLinkedMutableMap | 5 | 10.200 | 32.284 | 27 | 110 |
| HashMap | 5 | 17.960 | 59.152 | 60 | 136 |
| Object2ObjectOpenHashMap | 5 | 18.532 | 76.600 | 77 | 127 |
| TypedLinkedMutableSyncMap | 5 | 26.404 | 33.596 | 27 | 112 |
| ConcurrentHashMap | 5 | 17.696 | 96.044 | 64 | 82 |
| Object2ObjectOpenHashSyncMap | 5 | 33.793 | 88.491 | 85 | 123 |
| TypedLinkedMutableMap | 54 | 53.611 | 71.444 | 22 | 122 |
| HashMap | 54 | 18.777 | 67.870 | 49 | 101 |
| Object2ObjectOpenHashMap | 54 | 20.944 | 75.925 | 37 | 117 |
| TypedLinkedMutableSyncMap | 54 | 64.001 | 73.796 | 22 | 115 |
| ConcurrentHashMap | 54 | 19.387 | 196.722 | 58 | 123 |
| Object2ObjectOpenHashSyncMap | 54 | 36.277 | 84.537 | 38 | 181 |
| TypedLinkedMutableMap | 180 | 146.572 | 166.583 | 22 | 52 |
| HashMap | 180 | 20.311 | 58.244 | 41 | 91 |
| Object2ObjectOpenHashMap | 180 | 24.775 | 68.227 | 23 | 142 |
| TypedLinkedMutableSyncMap | 180 | 160.616 | 168.050 | 22 | 54 |
| ConcurrentHashMap | 180 | 20.600 | 157.194 | 47 | 114 |
| Object2ObjectOpenHashSyncMap | 180 | 40.550 | 69.922 | 23 | 129 |