``` /** * A semi-persistent mapping from keys to ...
# coroutines
g
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/**
 * A semi-persistent mapping from keys to values. Cache entries are manually added using
 * {@link #get(Object, Callable)} or {@link #put(Object, Object)}, and are stored in the cache until
 * either evicted or manually invalidated.
 *
 * <p>Implementations of this interface are expected to be thread-safe, and can be safely accessed
 * by multiple concurrent threads.
 *
 * @author Charles Fry
 * @since 10.0
 */
a good intro here: https://github.com/google/guava/wiki/CachesExplained