class CollectionUtils {

    public static List<String> toUpperList(List<String> sourceList) {
        if (isEmpty(sourceList)) { return sourceList; }
        List<String> destList = new ArrayList<>(sourceList.size());
        for (String element : sourceList) {
            if (element != null) {
                destList.add(element.toUpperCase());
            } else {
                destList.add(null);
            }
        }
        return destList;
    }

    private  CollectionUtils();

}