public boolean contains(@CheckForNull Object o) {
      refreshIfEmpty();
      return delegate.contains(o);
    }

    @Override
    public boolean containsAll(Collection<?> c) {
      refreshIfEmpty();
      return delegate.containsAll(c);
    }

    @Override
    public void clear() {
      int oldSize = size(); // calls refreshIfEmpty
      if (oldSize == 0) {
        return;
      }

    public boolean contains(@CheckForNull Object o) {
      refreshIfEmpty();
      return delegate.contains(o);
    }

    @Override
    public boolean containsAll(Collection<?> c) {
      refreshIfEmpty();
      return delegate.containsAll(c);
    }

    @Override
    public void clear() {
      int oldSize = size(); // calls refreshIfEmpty
      if (oldSize == 0) {
        return;
      }