1. It would be nice to introduce a covariance/contravariance in types:

    public void insert<T>(T item, List<? super T> list) {
        list.add(item); // Ok. If list have type List<G> then T is subtype of G
    }

    public void T get_random<T>(List<? extends T> list) {
        int elem = rand.rand_int (0, list.size);
        return list.get(elem); // Ok. If list have type List<G> then G is subtype of T
    }

2. It would be nice to allow restriction on arguments:

public abstract MyCollection<C extends Collection<int>> {
    public MyCollection(C c) {
        c.add(0); // Ok. C is Collection<int> so we can call add
    }
    public C col;
}

List<int> l = new ArrayList<int>();
MyCollection<List<int>> c = new MyCollection<List<int>>(l);
List<int> l2 = c.col; // Ok. c.col have type List<int>