返回List <t>或Set <t>的Collection <t>的java泛型

Question

我正在尝试编写一个实现Enumeration>的类，以便根据我想要的获取的不是Collection，而是Set或List...。

我希望能够使用以下语法：

Enumeration<Set<Integer>> setEn =
    new CollectionEnumeration<Integer, Set<Integer>>(ids, HashSet.class);

或：

Enumeration<Set<Integer>> setEn =
    new CollectionEnumeration<Integer, Set>(ids, HashSet.class);

或：

Enumeration<List<Integer>> listEn =
    new CollectionEnumeration<Integer, List<Integer>>(ids, ArrayList.class);

或：

Enumeration<List<Integer>> listEn =
    new CollectionEnumeration<Integer, List>(ids, LinkedList.class);

声明类的正确方法是什么？

这是我到目前为止所拥有的：

class CollectionEnumeration<T, Coll extends Collection<T>> implements Enumeration<Coll> {
    final private List<List<T>> stopListZoneIds;
    final private Class<? extends Coll> klass;
    final private int[] index;
    final private int max;
    private int current;
    private int stopIndex;

    CollectionEnumeration(List<List<T>> stopListZoneIds, Class<? extends Coll> klass) {
        this.stopListZoneIds = stopListZoneIds;
        this.klass = klass;
        int all = 1;
        index = new int[stopListZoneIds.size()];
        for (int stopIdx = 0; stopIdx < stopListZoneIds.size(); stopIdx++) {
            index[stopIdx] = 0;
            all *= stopListZoneIds.get(stopIdx).size();
        }
        max = all;
        current = 0;
        stopIndex = 0;
    }

    @Override
    public boolean hasMoreElements() {
        return current < max;
    }

    @Override
    public Coll nextElement() {
        if (!hasMoreElements()) {
            return null;
        }
        try {
            Coll collection = klass.newInstance();
            for (int stopIdx = 0; stopIdx < stopListZoneIds.size(); stopIdx++) {
                collection.add(stopListZoneIds.get(stopIdx).get(index[stopIdx]));
            }
            doStep();
            return collection;
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    private void doStep() {
        if (current >= max) {
            throw new RuntimeException("Shouldn't call doStep() when !hasMoreElements()");
        }
        do {
            if (index[stopIndex] < stopListZoneIds.get(stopIndex).size()) {
                index[stopIndex]++;
                current++;
                return;
            } else {
                index[stopIndex] = 0;
                stopIndex++;
            }
        } while(stopIndex < stopListZoneIds.size());
        current++;
    }
}