如果要你自己实现一个链表，实现数据的增删改查，需要怎么做？

class Node {
    private Object obj;
    Node next;
    public Node(Object obj) {
        this.obj = obj;
    }
    public Object value() {
        return obj;
    }
}
public class LinkedList {
    private Node head;
    private Node tail;
    private int size;
    public void add(Object obj) {
        Node node = new Node(obj);
        if (null == tail) {
            head = node;
            tail = node;
        } else {
            tail.next = node;
            tail = node;
        }
        size ++;
    }
    public Object get(int index) {
        if (null == head) return null;
        Node current = head;
        for (int i = 0; i <= index; i ++) {
            if (null == current) return null;
            if (i == index) {
                return current.value();
            }
            current = current.next;
        }
        return null;
    }
    public int size() {
        return size;
    }
}