//在链表尾部加入新节点
public class Node{
    public int data;
    public Node next;
    public Node(int data){
        this.data=data;
    }
}
public void addNode(int n){
    Node newNode=new Node(n);
    if(head==null){
        head=newNode;
        return;
    }
    Node tmp=head;
    while(tmp.next!=null){
        tmp=tmp.next;
    }
    tmp.next=newNode;
}