Timeout hashtable Java

Question

I'm still learning programming and came across an interesting task I must do. Your help will be much appreciated as i have no idea how to implement such task and i have been battling with it for a couple of days now...

A class which stores elements in a Hashtable for a defined amount of time. After the time runs out, the value and key must be deleted. Accessing or manipulating a value, resets the timer for that value. All i managed to figure out was use a timer, but I have no idea where to start from . I can't use anything else like Guava MapMaker suggested in other answers.

I'd appreciate your ideas and help guys!

Answer 1

Create a class with a concurrent Hashmap with methods like put, get and remove.

When putting a element, add it to the map and schedule a runnable to remove it after a amount of time. See the SchedulerExecutorService class to do that.

The submit() method of the executor service returns a Future which lets you to cancel the removing process if necessary.

Answer 2

If rolling-your-own solution this will likely involve storing entries in a ConcurrentMap which have a timestamp. You'll then likely have a scheduled job (see ScheduledExecutorService ) which removes stale entries.

This problem has been solved many times by many cache implementations. See Guava's CacheBuilder for one such implementation.