if (index < 0 || index > size()) {
if (index < 0 || index > size()-1) {
public int intAt(int index) {    if (index < 0 || index > size()) {        throw new IndexOutOfBoundsException();    }//    int pageNum = (int) index / pageSize;    int pageNum = index>>exp;    //System.out.println("page Number is "+pageNum); //    int offset = index % pageSize;    int offset = index & r;    return ((int[]) bufferArrayList.get(pageNum))[offset];}