Java 8 Collector for a Guava ImmutableList

ImmutableListCollector.java

public final class ImmutableListCollector {
    
    public static <T> Collector<T, ImmutableList.Builder<T>, ImmutableList<T>> toImmutableList() {
        return Collector.of(
            ImmutableList::builder,
            ImmutableList.Builder::add,
            (left, right) -> { left.addAll(right.build()); return left; },
            ImmutableList.Builder::build);
    }
    
}