class CollectionUtilities {

    public static <T> Collection<T> difference(Collection<? extends T> col1, Collection<? extends T> col2)
    {
        Collection<T> diff;
        if (col2.isEmpty())
        {
            diff = New.list(col1);
        }
        else
        {
            diff = New.list(col1.size());
            if (!col1.isEmpty())
            {
                for (T item : col1)
                {
                    if (!col2.contains(item))
                    {
                        diff.add(item);
                    }
                }
            }
        }
        return diff;
    }

    private  CollectionUtilities();

}