What is a simple way to Cache a List (or other Collection) in Java

Question

I have a Collection in the form of a List pulled out of the database that will never change once it is pulled; every user in the system will see the same thing. I have been trying to figure out the simplest way to cache it. I know I can use CacheBuilder from Guava, but it seems like overkill to create a cached map with 1 item in it that never changes.

hmm just keep that list somewhere in memory in one of your objects? — Amin J, Sep 27 '16 at 18:36
Guava's `Suppliers.memoize()` is preferred for single item caches. — Ben Manes, Sep 27 '16 at 18:54
@BenManes That is exactly what I was looking for, and worked perfectly. — Kraagenskul, Sep 27 '16 at 20:30
Since this was written, Ben Manes has written the Caffeine Caching system. Wonder if the guava example is still the best, or using Caffeine with a constant string as the key? — Michael Rountree, Mar 18 '21 at 16:53

score 4 · Accepted Answer · answered Sep 27 '16 at 20:33

From @BenManes above, I used Suppliers.memoize:

private Supplier<Collection<Person>> cache = Suppliers.memoizeWithExpiration(
        new Supplier<Collection<Employee>>() {
            public Collection<Employee> get() {
                return getAllEmployees();
            }
        }, 1, TimeUnit.DAYS);

public Collection<Employee> getAllEmployees() {
    return cache.get();
}

What is a simple way to Cache a List (or other Collection) in Java

1 Answers1

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