I'm using Guava's Immutable collections. Basically I have two helper functions that return ImmutableSets both of which contain data that are instances of inner classes that implement a common interface. However, I want to merge the two Immutable sets in order into a single ImmutableSet, in the actual function.
private static ImmutableSet<Fruit.seedless> helper1(args...) {...}
private static ImmutableSet<Fruit.seeded> helper2(args...) {...}
public ImmutableSet<Fruit> MainFunction() {...}