Class that describes a immutable, ordered set

Question

I need some class/interface name that describes an immutable, ordered set (in input order, like LinkedHashSet). I can of course just use the class like this:

class Foo {
    public final Set<Long> frozenOrderedSet;

    public Foo(List<Long> input) {
        frozenOrderedSet = Collections.unmodifiableSet(new LinkedHashSet(input));
    }
}

But this would not clarify my approach. I would like to make it clear to everyone reading the source that the Set is unmodifiable and unique while maintaining it's order with for(Long l : set){}.

Answer 1

Guava's ImmutableSet provides a high-performance, immutable Set with reliable, user-specified iteration order. There are also variations like ImmutableSortedSet.

Answer 2

The simplest way would be extend Set to create a custom immutable Set.

public CustomImmutableSet(){ return Collections.unmodifiableSet(new LinkedHashSet(input)); }

This way it will make it clear to everyone reading the source that the Set is unmodifiable and unique