Leandro Rosa

Guava Cache with Java 8 Lambdas

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Today I needed to cache some values in memory in an application that does a lot of json parsing and I tought that Guava Cache would be nice for that.

Creating the cache

To create the cache we use a CacheBuilder and setup the properties in it.

private static final Cache<Integer, String> cache =
      CacheBuilder.newBuilder()
          .weakValues()
          .maximumSize(CACHE_SIZE)
          .build(
              new CacheLoader<Integer, String>() {
                @Override
                public String load(Integer key) throws Exception {
                  return "my computed value";
                }
              });

Sounds a little bit verbose, maybe we can use Jaba 8 lambdas instead of the CacheLoader?

Using Java 8 lambdas

There’s a way you can separate the creation of the cache from it’s use, so you can isolate the cache configuration from the business logic.

Creation:

private static final Cache<Integer, String> cache =
      CacheBuilder.newBuilder()
          .weakValues()
          .maximumSize(CACHE_SIZE)          
          .build();

Using the cache:

cache.get(key, () ->  "my computed value");

Much more cleaner :)

Reference