自己用java实现LinkList和arrayList

为了加深理解，我就自己写了下LinkList和arrayList。
下面贴下代码

链表代码

public class MyTwoLinkedList<AnyType> implements Iterable<AnyType> {
    private int theSize;
    private int modCount = 0;
    private Node<AnyType> beginMarker;
    private Node<AnyType> endMarker;

    private static class Node<AnyType> {
        public AnyType data;
        public Node<AnyType> prev;
        public Node<AnyType> next;

        public Node(AnyType d, Node<AnyType> p, Node<AnyType> n) {
            data = d;
            prev = p;
            next = n;
        }
    }

    public MyTwoLinkedList() {
        clear();
    }

    public void clear() {
        beginMarker = new Node<AnyType>(null, null, null);
        endMarker = new Node<AnyType>(null, beginMarker, null);
        beginMarker.next = endMarker;

        theSize = 0;
        modCount++;
    }

    public int size() {
        return theSize;
    }

    public Boolean add(AnyType x) {
        add(size(), x);
        return true;
    }

    public void add(int idx, AnyType x) {
        addBefore(getNode(idx), x);
    }

    //搜索节点，先判断节点在前半段还是后半段，略提高效率，双链表可以从两个方向查找
    private Node<AnyType> getNode(int idx) {
        Node<AnyType> p;//一个引用

        if (idx < 0 || idx > size())
            throw new IndexOutOfBoundsException();