Types being referred to by non-canonical names can be confusing. For example,

public final class Entries {
  private final ImmutableList<ImmutableMap.Entry<String, Long>> entries;

  public Entries(Map<String, Long> map) {
    this.entries = ImmutableList.copyOf(map.entrySet());
  }
}

There is nothing special about ImmutableMap.Entry; it is precisely the same type as Map.Entry. This example makes it look deceptively as though ImmutableList<ImmutableMap.Entry<?, ?>> is an immutable type and therefore safe to store indefinitely, when really it offers no more safety than ImmutableList<Map.Entry<?, ?>>. You should use ImmutableList<Map.Entry<?, ?>> instead, so it's obvious what type you're referring to.