链表的增删改查（Java编程）

public class linked {
    private Node head;
    private Node last;
    private int size;
    public linked(){
        size = 0;
    }
    public linked(Node head,Node last){
        this.head = head;
        this.last = last;
        head.next = last;
        size = 2;
    }
    public void insert(Node node,int index)throws Exception{
        if (index<0||index>size){
            throw new Exception("链表越界");
        }
        //如果还没有初始化
        if (size == 0){
            this.head = node;
            this.last = node;
        }
        //插在尾部
        else if (index==size){
            last.next = node;
            last = last.next;
        }
        //插在头部
        else if (index == 0){
            node.next = head;
            head = node;
        }
        //插在中间
        else{
            node.next = getNode(index-1).next;
            getNode(index-1).next = node;
        }
        size++;
    }
    public void delete(int index)throws Exception{
        if (index<0||index>size){
            throw new Exception("链表越界");
        }
        if (index == 0){
            head = head.next;
        }
        else if (index == size-1) {
            getNode(index - 1).next = null;
            last = getNode(index - 1);
        }
        else{
            getNode(index-1).next = getNode(index).next;
        }
        size--;
    }
    public Node getNode(int index){
        int i = 0;
        Node n1 = head;
        while(true){
            if (i == index){
                return n1;
            }
            n1 = n1.next;
            i++;
        }
    }
    public void update(int index,String date){
        getNode(index).date = date;
    }


    public void output(){
        Node n1 = head;
        for (int i = 0; i < size; i++) {
            System.out.println(n1+" ");
            n1 = n1.next;
        }

    }

    public static void main(String[] args)throws Exception {
        Node n1 = new Node("1号");
        Node n2 = new Node("2号");
        Node n3 = new Node("3号");
        Node n4 = new Node("4号");
        Node n5 = new Node("5号");
        Node n6 = new Node("6号");
        linked linked1 = new linked(n1, n5);
        linked1.insert(n2,1);
        linked1.insert(n3,2);
        linked1.insert(n4,3);
        linked1.insert(n6,0);
        linked1.update(0,"0号");
        linked1.output();
        linked1.delete(0);
        linked1.delete(2);
        linked1.delete(3);
        linked1.output();
    }

}
class Node{
    String date;
    Node next;
    public Node(){}
    public Node(String date,Node next){
        this.date = date;
        this.next = next;
    }
    public Node(String date){
        this.date = date;
    }


    @Override
    public String toString() {
        return date;
    }
}