@Synchronized fun get(key: K, useCache: Boolean = true): V
Returns the value that corresponds to key.
If it does not exist, it is instantiated and then returned. If useCache is set to false, a new value is always
instantiated, even if there already is a value for key.
key - the key to look up the value with
useCache - whether to return the existing value if it exists
Return
the value that corresponds to key