Return singleton empty list if zero copies requested in Collections::nCopies

A DESCRIPTION OF THE PROBLEM :
There exists in the Collections class a method called "nCopies". Optimize this method to return Collections.emptyList() if n equals 0 to avoid instantiating an empty CopiesList object.

    public static <T> List<T> nCopies(int n, T o) {
        if (n < 0)
            throw new IllegalArgumentException("List length = " + n);
        return new CopiesList<>(n, o);
    }