The Cache interface.

abstract class Cache<K, V> {
 /**
  * Returns the value for `key` from the cache.  If `key` is not in the cache,
  * returns `null`.
  */
 V get(K key);
 /**
  * Inserts/Updates the `key` in the cache with `value` and returns the value.
  */
 V put(K key, V value);
 /**
  * Removes `key` from the cache.  If `key` isn't present in the cache, does
  * nothing.
  */
 V remove(K key);
 /**
  * Removes all entries from the cache.
  */
 void removeAll();
 int get capacity;
 int get size;
 CacheStats stats();
}