I have 2 distinct types of persistent values that I'm having trouble naming well.

They're defined with the following Java-esque structure, borrowing Guava's Optional for the example and using generic names to avoid anchoring:

interface Foo<T> {
    T get();
    void set(T value);
}

interface Bar<T> {
    Optional<T> get();
    void set(T value);
}

• With Foo, if the value hasn't been set explicitly then there's some default value available or pre-set.
• With Bar, if the value hasn't been set explicitly then there's a distinct "no value" state.

I'm trying to optimize the names for their call sites. For example, someone using Foo may not care whether there's a default value involved, only that they're guaranteed to always have a value.

How would you go about naming these interfaces?