How to use Guava Cache with expiry time for an ArrayList?

Question

I just found out about Guava Caching, and all the examples that I see are using map, key, and value.

Is there any way to use guava cache for an ArrayList?

I have an ArrayList that has elements, each element has 60 seconds to live, after that it should be removed, I appreciate any suggestions.

And is it possible to trigger a method after removal of each element? For example, if a number gets removed from the list I need to recalculate the average again.

Answer 1

Is there any way to use guava cache for an ArrayList?

Guava Cache is designed to be queried by key. However, you could use index of your ArrayList as a key or choose some unique property of the object to be the key (though as I understand, you need the values to be stored in the order they were added).

And is it possible to trigger a method after removal of each element?

Yes, when building your Cache<K, V>, set RemovalListener<K,V>.

For example:

Cache<String, String> cache = CacheBuilder.newBuilder()
    .expireAfterWrite(60, TimeUnit.SECONDS)
    .removalListener(new RemovalListener<String, String>() {
      public void onRemoval(RemovalNotification<String, String> removal) {
        // Compute the average here
      }          
    })
    .build();