ScheduledExecutorService performance

Question

I have a list of objects whose maximum size is 5000. When an object has not been updated for a type specific amount of time like 5, 10 or 100 seconds, it will be deleted from the list.

What is the best or preferred option to handle such a situation?

• Using a scheduled task for each object update. Cancelling old one and reset the new one.

• Or using one scheduled task with fixed delay say 500 ms. Checking the old objects via time comparison...

• or something else.

What do you recommend?

Answer 1

If you can use Google's Guava, you should give the Cache class a try.

For example, you could have one cache for each type of object:

LoadingCache<String, ObjectOfType1> type1Cache = CacheBuilder.newBuilder()
   .maximumSize(5000)
   .expireAfterWrite(5, TimeUnit.SECONDS)
   .removalListener(MY_LISTENER)
   .build(
       new CacheLoader<String, ObjectOfType1>() {
         public Graph load(String key) throws AnyException {
           return createExpensiveGraph(key);
         }
       });

And for Type2:

LoadingCache<String, ObjectOfType2> type2Cache = CacheBuilder.newBuilder()
   .maximumSize(5000)
   .expireAfterWrite(10, TimeUnit.SECONDS)
   .removalListener(MY_LISTENER)
   .build(
       new CacheLoader<String, ObjectOfType2>() {
         public Graph load(String key) throws AnyException {
           return createExpensiveGraph(key);
         }
       });

Then, you could just use a cache as if it were a Map:

ObjectOfType1 o1 = type1Cache.get("1");
ObjectOfType2 o2 = type2Cache.get("2");