Great and simple solution.

Here’s what I understood from you. Below is what I think should work now. Correct me if I’m wrong.

private Runnable createRemoveRunnable(final String name)
    {
        return new Runnable()
        {
            public void run()
            {
                synchronized (this)
                {
                    objects.remove(name);
                    expire.remove(name);
                }
            }
        };
    }

How do you modify the code as Vladislav mentioned to prevent ConcurrentModificationAccessException from happening during the expiration removal process?

Will this work (adding synchronized keyword to the run method)?

public synchronized void run() {
for (final String name : expire.keySet()) {
…
…
}
}

The approach I used to implement a cache like yours was to use java.util.LinkedHashmap. This offers functionality to set a limit to the size of the cache and remove the least recently used item from the cache when the limit is exceeded. Advantages are that you don’t need a scheduled worker thread to clean up your cache and the maximum size of the cache can be pre-determined.