使用泛型自定义类时的ClassCastException

class vector<E> {
    static int MAX_LEN = 1234567;
    E[] data;
    int[] prv;
    int to;
    int size;

    vector() {
        data = (E[])new Object[MAX_LEN];
        prv = new int[MAX_LEN];
        to = -1;
        size = 0;

        for(int i = 0; i < MAX_LEN; ++i) {
            prv[i] = -1;
        }
    }

    void push_back(E e) {
        data[size] = e;
        prv[size] = to;
        to = size;
        ++size;
    }
}

public class Main {

    public static void main(String[] args) throws Exception {
        vector<Integer> v = new vector();
        v.push_back(1);
        v.push_back(2);
        v.push_back(3);
        v.push_back(4);
        v.push_back(5);

        for(int i = v.to; i != -1; i = v.prv[i]) {
            System.out.println(v.data[i]); //<- Exception here
        }
    }
}