README.md

TinyMap

Memory-Efficient Immutable HashMaps

This library provides a straightforward open-addressing ordered hash table implementation. That implementation, along with an aggressive caching strategy (also provided here) can lead to incredibly low memory usage for semi-structured hashmaps.

That is very useful to represent small immutable events.

Usage

TinyMap is available through Maven Central repository, just add the following dependency to your pom.xml file:

<dependency>
    <groupId>net.intelie.tinymap</groupId>
    <artifactId>tinymap</artifactId>
    <version>0.1</version>
</dependency>

Building a new map (without caches)

TinyMap<Object, Object> built = TinyMap.builder()
        .put("key1", "value1")
        .put("key2", TinyList.builder().add(42.0).add("subvalue").build())
        .build();

This map uses exactly 384 bytes in Java 8, considering all its object tree. This is already better than Guava's ImmutableMap (408 bytes) and LinkedHashMap (528 bytes).

Optimizing existing map (with cache)

TinyMap can leverage aggressive caching to avoid representing same maps, keySets, or even Strings multiple times.

ArrayList<Object> list = new ArrayList<>();

for (int i = 0; i < 1000; i++) {
    LinkedHashMap<String, Object> map = new LinkedHashMap<>();
    map.put("key1", "value" + i);
    map.put("key2", i);
    map.put("key3", (double)(i/100));
    list.add(map);
}

TinyOptimizer optimizer = new TinyOptimizer(new ObjectCache());
TinyList<Object> tinyList = optimizer.optimizeList(list);

The optimized version uses almost 60% less memory than the pure Java version (137.19 KB vs 348.75 KB).

Parsing JSON

TODO